DE102019216820B4 - Liquid-cooled internal combustion engine with at least one cylinder tube - Google Patents

Abstract

Liquid-cooled internal combustion engine with- at least one cylinder head with at least one cylinder (3), and- at least one cylinder block connected to the at least one cylinder head and serving as the upper half of the crankcase for accommodating at least one piston (1), in which- each cylinder (3) has a combustion chamber (3b), which is formed by the cylinder-associated piston (1), a cylinder tube (2) and the at least one cylinder head, the piston (1) along a longitudinal cylinder axis (3a) between a top dead center OT and a bottom dead center UT is translationally displaceable to form a piston stroke s,- the cylinder block being equipped with liquid cooling, the cylinder block being equipped with at least one integrated coolant jacket (5) to form liquid cooling,- wherein a wall (2a) of the cylinder tube (2) belonging to the cylinder at least one coolant jacket (5) at least in some areas with limited, in such a way that an outside (2b) of the cylinder tube (2) is acted upon by coolant (5a), and- a wall thickness w of the wall (2a) starting from top dead center OT along the cylinder longitudinal axis (3a) towards the bottom Dead center UT first increases and then decreases again, - with the wall thickness (w) of the wall (2a) varying on a circumference around the cylinder longitudinal axis (3a), characterized in that the wall thickness w - promoting heat dissipation - in an upper, the upper Dead center OT facing section is smallest, in a middle section having a lower heat dissipation relative to the upper section, it is greatest and in a lower section facing lower dead center UT - a heat dissipation relative to the middle section favoring - is dimensioned decreasing again.

Description

The invention relates to a liquid-cooled internal combustion engine having the features of the preamble of claim 1.

From the DE 10 2011 085 476 A1 a cylinder liner intended for a generic internal combustion engine is known, with a liner that is also cylindrical on the outside or also non-circular in design and is fixed in a cylinder housing by means of a collar. By far the largest axial section of the cylinder liner is located opposite a recess in the side facing the inner wall of the cylinder housing, thereby forming a gap for conducting a coolant. Sections of said inner wall adjoin this gap axially on both sides, each of which is intended to receive sealing rings.

From the DE 10 2010 017 378 A1 a cooling device for a cylinder liner and a cylinder block of an internal combustion engine is known, with a liner surrounding a liner and bearing positively on its outer lateral surface, a cooling device which encloses an annular cavity intended for guiding a coolant. This cavity is - viewed along the axis of the liner - set up with the proviso that, starting from a top dead center (TDC) of a piston movement in the direction of a bottom dead center (UT), there is a continuous reduction in its radial dimensions, so that in the area of the top Dead center is set up a relatively larger heat dissipation than at bottom dead center. The cooling device as such can be part of an aluminum cylinder or an aluminum cylinder block.

From the DE 198 45 347 C1 a cylinder liner is known which is intended for insertion into the cylinder bore of an engine block of an internal combustion engine. The liner is provided with different wall thicknesses in the circumferential direction, which are intended to increase strength and reduce the occurrence of thermally induced distortions. The different wall thicknesses are formed by local material accumulations such as ribs or the like.

From the U.S.A. 4,399,783 a cylinder block for receiving the piston of an internal combustion engine is known, in which a cylinder liner is inserted, which is secured in the installed position by a press fit. In a central section, the bushing has an increased wall thickness which is, however, completely uniform in the axial direction, with a recess in the cylinder block opposite this section, in this case forming a space for conducting a coolant. On both sides of this section there are sections with a smaller wall thickness, which in both cases are only intended for accommodating sealing rings.

From the U.S. 6,044,821A a liner for the piston of an internal combustion engine is known, which consists of two different parts connected to one another by friction welding, with a first part having a section with a significantly increased wall thickness on its end, an upper section of the liner, here facing the top dead center. This section forms an annular formation which is intended to positively secure the position of the liner when inserted in a cylinder block. In any case, a second part has a significantly reduced wall thickness compared to the facing section of the first part.

From the DE 10 2017 200 047 A1 a modular cylinder block for an internal combustion engine is known. The use of an additive manufacturing process to produce a cylinder tube, for example by means of 3D printing, is mentioned.

the DE 197 45 585 A1 relates to an internal combustion engine having at least one cylinder, a piston reciprocating in the cylinder, a cylinder liner for guiding the piston, and a cooling water space disposed radially outside a cooling portion of the cylinder liner. The cooling section of the cylinder liner is divided into three areas in the axial direction: an area with small thermal resistance, an area with large thermal resistance, and a transition area in between with gradually increasing thermal resistance.

A liquid-cooled internal combustion engine is also in the U.S.A. 4,399,783 , the EP 2 604 835 A1 as well as the U.S. 2,120,004A described and used according to the prior art, for example as a motor vehicle drive. In the context of the present invention, the term internal combustion engine refers to diesel engines and Otto engines, but also hybrid internal combustion engines, i.e. internal combustion engines that are operated with a hybrid combustion process, and hybrid drives that, in addition to the internal combustion engine, use at least one other torque source to drive a motor vehicle include, for example, an electric machine which can be drive-connected or is drive-connected to the internal combustion engine and which delivers power instead of the internal combustion engine or in addition to the internal combustion engine.

Internal combustion engines have a cylinder block and at least one cylinder head, which can be connected to one another or are connected to one another to form the individual cylinders, ie combustion chambers. The individual components are briefly discussed below.

The cylinder head serves to accommodate the control elements and, in the case of an overhead camshaft, to accommodate the valve trains as a whole. During the gas exchange, the combustion gases are expelled via the at least one outlet opening and the combustion chamber is filled via the at least one inlet opening of each cylinder. In four-stroke engines, lifting valves are almost exclusively used as control elements to control the gas exchange, which perform an oscillating lifting movement during operation of the internal combustion engine and in this way open and close the inlet opening or outlet opening. The valve actuation mechanism, including the valve itself, required to move a valve is called the valve train.

In the case of spark-ignited internal combustion engines, the required ignition device can also be arranged in the cylinder head, and in the case of direct-injection internal combustion engines the injection device can also be arranged. In order to form a functional connection between the cylinder head and the cylinder block that seals the combustion chambers, a sufficient number and sufficiently large bores must be provided.

The cylinder block has a corresponding number of cylinder bores or cylinder liners to accommodate the pistons. The piston of each cylinder of an internal combustion engine is guided in a cylinder tube so that it can move axially along the longitudinal axis of the cylinder and, together with the cylinder tube and the cylinder head, delimits the combustion chamber of a cylinder. The piston crown forms part of the inner wall of the combustion chamber and, together with the piston rings, seals the combustion chamber against the cylinder block or crankcase, so that no combustion gases or combustion air can get into the crankcase and no oil can get into the combustion chamber. The cylinder tube is formed either using a cylinder liner insertable into the cylinder block or directly through the cylinder block itself, namely the cylinder bore.

The pistons serve to transfer the gas forces generated by the combustion to the crankshaft. For this purpose, each piston is connected in an articulated manner by means of a piston pin to a connecting rod, which in turn is movably mounted on the crankshaft.

The crankshaft mounted in the crankcase absorbs the connecting rod forces, which are made up of the gas forces resulting from fuel combustion in the combustion chamber and the inertial forces resulting from the non-uniform movement of the engine parts. The oscillating stroke movement of the pistons is transformed into a rotating rotary movement of the crankshaft. The crankshaft transmits torque to the drive train. Part of the energy transmitted to the crankshaft is used to drive auxiliary units such as the oil pump and alternator, or is used to drive the camshaft and thus actuate the valve trains.

In general, and within the scope of the present invention, the upper crankcase half is formed by the cylinder block. The crankcase is regularly supplemented by the lower half of the crankcase, which can be mounted on the upper half of the crankcase and serves as an oil pan.

The cylinder block of an internal combustion engine is a component subject to high thermal and mechanical loads, and the demands on the cylinder block are increasing. In this context, it must be taken into account that internal combustion engines are increasingly being supercharged - for example by means of exhaust gas turbochargers or mechanical or electrical superchargers - in order to reduce fuel consumption, i.e. to improve efficiency. This increases both the thermal and the mechanical stress on the internal combustion engine or the cylinder block, so that increased demands are placed on the cooling and the other components of the cylinder block and measures must be taken to cope with the thermal and mechanical stress.

In principle, there is the possibility of cooling the motor in the form of air cooling or liquid cooling. In the case of air cooling, the internal combustion engine is provided with a fan, the heat being removed by means of an air flow guided over the surface of the cylinder head and the cylinder block.

Due to the higher thermal capacity of liquids compared to air, significantly larger amounts of heat can be dissipated with liquid cooling than is possible with air cooling. For this reason, internal combustion engines are increasingly being equipped with liquid cooling.

The internal combustion engine, which is the subject of the present invention, has liquid cooling, with at least the cylin The block is equipped with liquid cooling.

Liquid cooling requires the internal combustion engine or the cylinder block to be equipped with at least one integrated coolant jacket that guides the coolant through the cylinder block. The heat given off to the coolant is extracted again from the coolant, for example in a heat exchanger which is preferably arranged in the front-end area of the vehicle.

Unlike with air cooling, the heat does not first have to be conducted to the block surface in order to be dissipated, but is already given off to the coolant inside the cylinder block. The coolant is conveyed by means of a pump arranged in the coolant circuit so that it circulates. In this way, the heat given off to the coolant is dissipated from the interior of the cylinder block and withdrawn again from the coolant outside the cylinder block, for example by means of a heat exchanger and/or in some other way.

A water-glycol mixture mixed with additives is usually used as the coolant. Compared to other coolants, water has the advantage of being non-toxic, readily available and inexpensive, and also has a very high heat capacity, which makes water suitable for the extraction and removal of very large amounts of heat, which is generally regarded as advantageous.

Like the cylinder block, the cylinder head can also be equipped with one or more coolant jackets. The cylinder head is regularly the thermally more highly stressed component, since the head, in contrast to the cylinder block, is equipped with exhaust gas-carrying lines and the combustion chamber walls integrated in the head are exposed to hot exhaust gas longer than the cylinder tubes provided in the cylinder block. In addition, the cylinder head has a lower component mass than the block.

Equipping the cylinder block with liquid cooling and at least one coolant jacket in an operating internal combustion engine according to the prior art leads to large temperature gradients in the block, particularly in the land area, i.e. in the area between two adjacent cylinders. This is also due to the fact that the design of the cooling according to the prior art is not based on needs, but rather with regard to the manufacturing process of the cylinder block, which is regularly produced using the casting process, which strongly influences and limits the arrangement and shape of the coolant jackets .

The large temperature differences in the cylinder block result in a more or less large thermal distortion of the cylinder tube of a cylinder. This so-called bore distortion has several disadvantageous effects in practice.

In order to reduce bore distortion, according to the prior art, slots and/or smaller bores are made in the web area by machining the cylinder block. However, this measure only leads to a slight improvement, since the entire area between two adjacent cylinders cannot be processed. In addition, the highly stressed block is weakened in terms of its strength and durability.

So that the piston, in cooperation with the cylinder tube and the piston rings, can effectively seal the combustion chamber from the crankcase despite bore distortion, the prestressing forces of the rings are increased according to the prior art, but this also disadvantageously increases the friction or friction loss of the internal combustion engine.

In principle, however, efforts are being made to minimize the friction loss of an internal combustion engine in order to reduce fuel consumption and thus also pollutant emissions.

Ideally, the thermally and the mechanically caused distortion should mutually influence or complement each other in such a way that the cylinder tube assumes and has the desired shape or form during operation of the internal combustion engine.

Against the background of what has been said, it is an object of the present invention to provide a liquid-cooled internal combustion engine according to the preamble of claim 1, which is improved with regard to the thermally and mechanically caused distortion of the cylinder tube.

• - mindestens einem Zylinderkopf mit mindestens einem Zylinder, und
• - mindestens einem mit dem mindestens einen Zylinderkopf verbundenen und als obere Kurbelgehäusehälfte dienenden Zylinderblock zur Aufnahme mindestens eines Kolbens, bei der
• - jeder Zylinder einen Brennraum umfasst, der durch den zylinderzugehörigen Kolben, ein Zylinderrohr und den mindestens einen Zylinderkopf mit ausgebildet ist, wobei der Kolben entlang einer Zylinderlängsachse zwischen einem oberen Totpunkt OT und einem unteren Totpunkt UT unter Ausbildung eines Kolbenhubs s translatorisch verschiebbar ist,
• - wobei der Zylinderblock mit einer Flüssigkeitskühlung ausgestattet ist, wobei der Zylinderblock zur Ausbildung einer Flüssigkeitskühlung mit mindestens einem integrierten Kühlmittelmantel ausgestattet ist,
• - wobei eine Wandung des zylinderzugehörigen Zylinderrohres mindestens einen Kühlmittelmantel zumindest bereichsweise mit begrenzt, in der Art, dass eine Außenseite des Zylinderrohres mit Kühlmittel beaufschlagt ist, und
• - eine Wandstärke der Wandung ausgehend vom oberen Totpunkt OT entlang der Zylinderlängsachse hin zum unteren Totpunkt UT zunächst zunimmt und dann wieder abnimmt,
• - wobei die Wandstärke der Wandung auf einem Umfang um die Zylinderlängsachse herum variiert.

The object is achieved with a liquid-cooled internal combustion engine having the features of claim 1

• - at least one cylinder head with at least one cylinder, and
• - At least one connected to the at least one cylinder head and serving as the upper half of the crankcase cylinder block for receiving at least one piston, in which
• - Each cylinder includes a combustion chamber, which is formed by the cylinder-associated piston, a cylinder tube and the at least one cylinder head, the piston along a cylinder longitudinal axis between a top dead center and a bottom dead center Dead center UT is translationally displaceable, forming a piston stroke s,
• - wherein the cylinder block is equipped with liquid cooling, wherein the cylinder block is equipped with at least one integrated coolant jacket to form liquid cooling,
• - wherein a wall of the cylinder-associated cylinder tube at least partially delimits at least one coolant jacket, in such a way that an outside of the cylinder tube is acted upon by coolant, and
• - a wall thickness of the wall initially increases and then decreases starting from top dead center OT along the cylinder longitudinal axis towards bottom dead center UT,
• - Wherein the wall thickness of the wall varies on a circumference around the longitudinal axis of the cylinder.

According to the invention, the wall thickness--promoting heat dissipation--is thinnest in an upper section facing top dead center OT, greatest in a middle section with lower heat dissipation relative to the upper section, and in a lower section facing bottom dead center UT - A heat dissipation relative to the middle section favoring - dimensioned decreasing again.

In contrast to the prior art, the wall of a cylinder tube of the internal combustion engine according to the invention that is acted upon by coolant does not have a constant wall thickness, but rather a wall thickness that varies along the longitudinal axis of the cylinder. The wall thickness w between the top and bottom dead centers first increases and then decreases again.

This structural design or shaping leads to cooling of the cylinder tube as required, as explained below.

The section of the cylinder tube that faces the cylinder head has a wall with a smaller wall thickness, so that the heat dissipation from the combustion chamber via the wall into the coolant is facilitated and promoted. This takes account of the fact that this area is exposed to hot exhaust gas for a longer period of time and is therefore subject to particularly high thermal loads. This section of the cylinder barrel near top dead center requires and receives more cooling than other sections of the cylinder barrel.

Starting from this upper section, i.e. starting from top dead center, the wall thickness increases along the longitudinal axis of the cylinder and in the direction of bottom dead center, whereby this increase does not have to begin immediately at top dead center and also does not have to be continuous or linear, but rather gradually or can take place in leaps and bounds. The thicker wall in the middle section of the cylinder tube means that the cooling capacity is lower and less heat is dissipated. This is advantageous because the middle section regularly includes the area of the cylinder tube in which the oscillating piston reaches its highest speed and requires good lubrication. The lower heat dissipation in this area due to a greater wall thickness w leads to a higher-temperature, highly viscous oil on the inside of the cylinder tube facing the piston, as a result of which the friction loss is advantageously reduced.

Starting from the middle section, the wall thickness decreases again along the longitudinal axis of the cylinder and in the direction of the bottom dead center, whereby this decrease does not have to end immediately at the bottom dead center and does not have to be continuous or linear, but can take place in stages or abruptly. The less thick wall in the lower section of the cylinder tube leads to greater heat dissipation. This takes into account that the hot piston is slow in reversing its direction at bottom dead center and therefore stays in the bottom section for a comparatively long time.

The wall thickness w of the wall also varies circumferentially around the longitudinal axis of the cylinder, as already mentioned.

The object on which the invention is based is achieved with the internal combustion engine according to the invention, namely a liquid-cooled internal combustion engine is provided which is improved with regard to the thermally and mechanically caused distortion of the cylinder tube.

As already mentioned, the cylinder tube has an upper section, a middle section and a lower section. Reference is made to the statements already made regarding the individual sections.

In this context, embodiments of the liquid-cooled internal combustion engine are advantageous in which the wall thickness w in the lower section is greater than the wall thickness in the upper section.

Further advantageous embodiments of the liquid-cooled internal combustion engine according to the invention are discussed in connection with the dependent claims.

Embodiments of the liquid-cooled internal combustion engine are advantageous in which the wall thickness w of the wall is greatest in a range of 0.25s≦x≦0.75s, with s denoting the piston stroke between top dead center OT and bottom dead center UT and x the distance starting forms from top dead center OT.

Embodiments of the liquid-cooled internal combustion engine are advantageous in which the wall thickness w of the wall is greatest in a range of 0.35s≦x≦0.75s, with s denoting the piston stroke between top dead center OT and bottom dead center UT and x the distance starting forms from top dead center OT.

Embodiments of the liquid-cooled internal combustion engine are advantageous in which the wall thickness w of the wall is greatest in a range of 0.45s≦x≦0.7s, with s denoting the piston stroke between top dead center OT and bottom dead center UT and x the distance starting forms from top dead center OT.

Embodiments of the liquid-cooled internal combustion engine are advantageous in which the wall thickness w of the wall is greatest in a range of 0.45s≦x≦0.65s, with s denoting the piston stroke between top dead center OT and bottom dead center UT and x the distance starting forms from top dead center OT.

The values x to be preferably selected also depend on the relevant internal combustion engine in the individual case, in particular on the region of the cylinder tube in which the oscillating piston reaches its highest speed.

Embodiments of the liquid-cooled internal combustion engine are advantageous in which the cylinder tube of each cylinder is designed as a cylinder bore of the cylinder block.

Embodiments of the liquid-cooled internal combustion engine are advantageous in which the cylinder tube of each cylinder is a cylinder liner that is inserted into the cylinder block.

The two above embodiments differ in that on the one hand the piston is received and supported directly in the cylinder block, for which purpose a cylinder bore is used, and on the other hand a bush is provided for receiving the piston, this bush being received in the block.

In the context of the present invention, the term cylinder tube forms the generic term under which the designations or embodiments cylinder bore and cylinder liner can be subsumed.

In a further aspect of the invention, a method is shown with which the cylinder tube is produced using an additive manufacturing method, in which the cylinder tube is built up in layers.

What has already been said for the internal combustion engine also applies to the method.

Embodiments of the method are advantageous in which the cylinder tube is also produced at least by means of 3D printing.

• 1a schematisch in einer Seitenansicht und teilweise geschnitten das Fragment eines Zylinderblocks einer ersten Ausführungsform der Brennkraftmaschine umfassend einen Kolben mitsamt Kurbeltrieb sowie einen Teil des Zylinderrohres, und
• 1b schematisch und in einem Querschnitt senkrecht zur Zylinderlängsachse das Zylinderrohr der in 1a dargestellten ersten Ausführungsform der Brennkraftmaschine.

The invention is based on an embodiment and according to the 1a and 1b described in more detail. This shows:

• 1a schematically in a side view and partially sectioned, the fragment of a cylinder block of a first embodiment of the internal combustion engine comprising a piston together with the crank mechanism and a part of the cylinder tube, and
• 1b schematically and in a cross section perpendicular to the longitudinal axis of the cylinder, the cylinder tube in 1a illustrated first embodiment of the internal combustion engine.

1a shows a schematic side view and partially sectioned fragment of a cylinder block of a first embodiment of the liquid-cooled internal combustion engine, comprising a piston 1 together with a crank mechanism 4 and part of the cylinder tube 2.

The cylinder tube 2 of the cylinder block serves to accommodate the piston 1, the piston 1 being translationally displaceable along the longitudinal cylinder axis 3a between a top dead center OT and a bottom dead center UT, forming a piston stroke s. The piston 1 serves to transmit the gas forces generated by the combustion to the crankshaft, for which purpose the piston 1 is connected to the crankshaft in an articulated manner by means of a piston pin and a connecting rod. The crank drive 4 transforms the oscillating stroke movement of the piston 1 into a rotating rotary movement of the crankshaft.

The combustion chamber 3b of a cylinder 3 is formed by the piston 1 belonging to the cylinder, the cylinder tube 2 and the cylinder head (not shown).

To form the liquid cooling, the cylinder block is equipped with an integrated coolant jacket 5, with a wall 2a of the Cylinder tube 2 limits the coolant jacket 5 in such a way that an outside 2b of the cylinder tube 2 is acted upon by coolant 5a.

The wall thickness w of the wall 2a increases starting from the top dead center OT along the longitudinal cylinder axis 3a towards the bottom dead center UT and then decreases again. This form or shape of the cylinder tube 2 or the wall 2a leads to cooling of the cylinder tube 2 as required, as a result of which the thermally and mechanically induced distortion of the cylinder tube 2 is influenced in an advantageous manner.

In the upper section of the cylinder tube 2, which faces the cylinder head, the wall 2a has the smallest wall thickness w. This promotes heat dissipation from the combustion chamber 3b into the coolant 5a. This area of the cylinder tube 2 is subject to particularly high thermal loads. Starting from top dead center, the wall thickness w increases along the cylinder longitudinal axis 3a.

The wall thickness w is greatest in the middle section of the cylinder tube 2, i.e. the wall 2a is the thickest. As a result, the cooling capacity is lower and less heat is dissipated. This is advantageous with regard to the lubrication of the piston 1 and thus with regard to the friction loss.

Starting from the middle section, the wall thickness w decreases again along the cylinder longitudinal axis 3a. The less thick wall 2a in the lower section of the cylinder tube 2 leads to greater heat dissipation. The hot piston 1 remains at bottom dead center for a comparatively long time when it reverses direction.

The wall thickness w in the lower section is greater than the wall thickness in the upper section.

1b shows schematically and in a cross section perpendicular to the cylinder longitudinal axis 3a the cylinder tube 2 in 1a illustrated first embodiment of the internal combustion engine.

It can be seen that the wall thickness w of the wall 2a also varies on a circumference around the longitudinal axis 3a of the cylinder.

Reference List

1

Pistons

2

cylinder barrel

2a

wall of the cylinder tube

2 B

outside of the cylinder tube

3

cylinder

3a

cylinder longitudinal axis

3b

combustion chamber

4

crank drive

5

coolant jacket

5a

coolant

OT

Top Dead Center

subtitles

bottom dead center

s

piston stroke

w

Wall thickness

x

Distance starting from top dead center along the longitudinal axis of the cylinder

Claims (6)

Liquid-cooled internal combustion engine with - at least one cylinder head with at least one cylinder (3), and - at least one cylinder block connected to the at least one cylinder head and serving as the upper half of the crankcase for accommodating at least one piston (1), in which - each cylinder (3) has a combustion chamber (3b), which is formed by the cylinder-associated piston (1), a cylinder tube (2) and the at least one cylinder head, the piston (1) along a longitudinal cylinder axis (3a) between a top dead center OT and a bottom dead center UT is translationally displaceable to form a piston stroke s, - the cylinder block being equipped with a liquid cooling system, the cylinder block being equipped with at least one integrated coolant jacket (5) to form a liquid cooling system, - a wall (2a) of the cylinder tube (2) belonging to the cylinder at least one coolant jacket (5) at least partially ice with limited, in such a way that an outside (2b) of the cylinder tube (2) is acted upon by coolant (5a), and - a wall thickness w of the wall (2a) starting from top dead center OT along the cylinder longitudinal axis (3a) towards bottom dead center UT first increases and then decreases again, - with the wall thickness (w) of the wall (2a) varying on a circumference around the cylinder longitudinal axis (3a), characterized in that the wall thickness w - promoting heat dissipation - in an upper, the lowest in the section facing top dead center OT, greatest in a middle section having lower heat dissipation relative to the top section, and decreasing again in a lower section facing bottom dead center UT - promoting heat dissipation relative to the middle section. Liquid-cooled internal combustion engine claim 1 , characterized in that the wall thickness w of the wall (2a) is greatest in a range of 0.35s ≤ x ≤ 0.75s, where s denotes the piston stroke between top dead center OT and bottom dead center UT and x denotes the distance from forms top dead center OT. Liquid-cooled internal combustion engine according to one of the preceding claims, characterized in that the wall thickness w of the wall (2a) is greatest in a range 0.45s ≤ x ≤ 0.7s, where s is the piston stroke between top dead center OT and bottom dead center UT denotes and x forms the distance starting from top dead center OT. Liquid-cooled internal combustion engine according to one of the preceding claims, characterized in that the wall thickness w of the wall (2a) is greatest in a range 0.45s ≤ x ≤ 0.65s, where s is the piston stroke between top dead center OT and bottom dead center UT denotes and x forms the distance starting from top dead center OT. Liquid-cooled internal combustion engine according to one of the preceding claims, characterized in that the cylinder tube (2) of each cylinder (3) is designed as a cylinder bore of the cylinder block. Liquid-cooled internal combustion engine according to one of Claims 1 until 4 characterized in that the cylinder tube (2) of each cylinder (3) is a cylinder liner fitted in the cylinder block.

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