EP3339617B1 - Cylinder housing, method for producing a cylinder housing and casting core - Google Patents

Description

The invention relates to a cylinder housing for a reciprocating piston device and to a method for producing such a cylinder housing. The invention also relates to a reciprocating piston device with such a cylinder housing and an internal combustion engine with such a reciprocating piston device. The invention also relates to a casting core for use in the method for producing such a cylinder housing.

Internal combustion engines are mostly cooled by means of a cooling liquid which, conveyed by at least one coolant pump, circulates in a cooling system of the internal combustion engine that integrates the cooling jacket. The circulating coolant can dissipate thermal energy from the internal combustion engine to at least one ambient heat exchanger, in which the thermal energy is then given off to the ambient air, for example.

Most known internal combustion engines have cooling jackets which surround the individual cylinders at least partially with respect to the circumference and essentially completely with respect to the longitudinal extent. In most known internal combustion engines, a coolant inlet is integrated in the area of top dead center, in which the cyclical to-and-fro movement of the piston guided in the corresponding cylinder is reversed and a fuel-fresh gas mixture is burned in the vicinity Cylinder is initiated, while an integration of a coolant outlet is provided near the bottom dead center of the piston movement. By means of such a cooling jacket, the local cooling capacity requirement, which varies along the longitudinal extension of the cylinder or cylinders, cannot be optimally met, because if the cooling system, including the cooling jacket, is adequately dimensioned, the cooling capacity requirement in the area of the top dead center of the piston movement, which occurs in this area because the primary combustion processes are highest there, "overcooling", ie excessive cooling, can occur in the other areas. However, too low a temperature of a cylinder wall often leads to a relatively high viscosity of a lubricant that keeps the friction of the relative movement between the cylinder wall and the associated piston low and thus to comparatively high friction losses and relatively high wear during operation of the internal combustion engine.

In the publication " Water Jacket Spacer for Improvement of Cylinder Bore Temperature Distribution "by Matsutani et al. (SAE TECHNICAL PAPER SERIES 2005-01-1156 ) it is described that for the lowest possible friction over the entire stroke of a piston in a cylinder of an internal combustion engine, the temperature of the cylinder wall in an area encompassing the top dead center of the piston movement (starting from the upper end of the cylinder) should rise to a maximum value, this maximum value should then remain as constant as possible over the further course of the longitudinal extent, ie at least up to the bottom dead center of the piston movement. In order to achieve this, an insert that specifically reduces the free flow cross-section should be integrated into an otherwise conventionally designed cooling jacket in that section of the longitudinal extent of the cylinder in which a temperature that is as constant as possible is to be achieved for the cylinder wall.

Another possibility for targeted influencing of the cooling effect for a cylinder of an internal combustion engine is from the publication " Analysis of Piston Friction - Effects of Cylinder Bore Temperature Distribution and Oil Temperature "by Kimura et al. (SAE 2011-01-1746 ) known. This describes an internal combustion engine, the cylinders of which are each surrounded by three separate cooling jackets spaced apart from one another with respect to the longitudinal extent, through which different volume flows of the coolant can be conveyed, controlled via valves, depending on the local cooling power requirement.

Furthermore, from the DE 86 28 188 U1 an internal combustion engine is known in which cooling jackets are provided for the cylinders exclusively in the areas of both dead centers of the piston movements.

It is generally known that the cylinders of an internal combustion engine can each be delimited by a so-called cylinder liner, which in turn is each received in an associated receiving opening of a cylinder housing. Such cylinder liners can be designed as so-called "wet" cylinder liners, the outer walls of which with the walls of the associated receiving openings each delimit an annular gap which serves as a cooling jacket. Wet liners of this type have so far mainly been used in truck engines and large engines.

Cylinder liners, in which a plurality of self-contained or spiral-shaped encircling recesses are integrated, which are provided as cooling channels of an internal combustion engine comprising the cylinder liners, are from the DE 102 25 062 A1 , of the U.S. 5,211,137 , of the U.S. 5,207,189 , of the U.S. 5,199,390 , of the U.S. 3,086,505 , of the JP H05-18319 A , of the U.S. 2,464,462 , of the EP 0 488 810 A1 and the U.S. 2,959,163 A known.

The US 2005/0274333 A1 discloses a cylinder liner for an internal combustion engine with integrated cooling ducts which run parallel to the longitudinal axis of the cylinder liner.

The EP 0 952 325 A2 discloses an internal combustion engine having a crankcase with cylinders formed by cylinder liners. Furthermore, a "cooling jacket" which surrounds the cylinder liners, represents a separate component and accommodated in the crankcase is provided. In the inner sides of the cooling jacket, partially circumferential grooves are formed which, in conjunction with the outer sides of the cylinder liners, each form a cooling channel for the cylinder. The cooling channels, which are separated from one another by a web formed by the adjacent cylinder liners, can have a spiral or meandering course.

The US 2010/0300394 A1 describes a cylinder housing with a plurality of cylinders, each of which is assigned a cooling jacket in the form of a single, spiral-shaped cooling channel. A series connection of the individual cooling jackets is provided in such a way that an outlet of the cooling channel of a first cooling jacket merges into an inlet of the cooling channel of an adjacent, second cooling jacket.

The invention was based on the object of specifying a cylinder housing integrating cooling channels for a reciprocating piston device and in particular for an internal combustion engine, an advantageous cooling effect being achieved for the cylinder housing with the most compact dimensions possible.

This object is achieved by means of a cylinder housing according to patent claim 1. A method for producing a cylinder housing according to the invention is the subject matter of claim 8 and a casting core for use in such a method is the subject matter of claim 10. Advantageous embodiments of the cylinder housing according to the invention and the casting core according to the invention as well as preferred embodiments of the method according to the invention are the subjects of the further claims and / or emerge from the following description of the invention.

According to the invention, a preferably one-piece cylinder housing for a reciprocating piston device and in particular for a (reciprocating piston) internal combustion engine is provided, which comprises at least two cylinders, each of which is provided for receiving a piston of the reciprocating piston device. The cylinder housing also has an integral cooling jacket for each of the cylinders (ie inside the cylinder housing and thus in particular not formed by cylinder liners), which surrounds the cylinder circumferentially in at least one longitudinally axial section, the cooling jackets each being divided into a plurality of closed circumferential cooling channels are divided and wherein a coolant inlet opens into at least one of the cooling jackets and a coolant outlet opens into at least one of the cooling jackets. Of the cooling channels, those that are assigned to different cylinders merge into one another between the cylinders.

As a result of this transition of the cooling channels assigned to the various cylinders into one another, an advantageous cooling effect can be achieved in the area of a separating web formed by the cylinder housing and separating adjacent cylinders, while at the same time the (minimum) width of the separating web integrating the cooling channels and thus also the distance between adjacent cylinders as possible can be kept low. This can have a correspondingly positive effect on the overall dimensions of the cylinder housing and a reciprocating piston device comprising such a cylinder housing and in particular a corresponding internal combustion engine. This is particularly true in comparison with a reciprocating piston device, in which cooling channels are formed by the interaction of recesses integrated in an outer side of cylinder liners with walls of receiving openings of a cylinder crankcase that receive the cylinder liners, because here the distances between the insides of adjacent cylinder liners provided for guiding the pistons each result from adding the width of a separating web provided between the receiving openings and twice the wall thickness of the cylinder liners.

In a cylinder housing according to the invention, it is further provided that a coolant inlet and a coolant outlet open into each of the cooling jackets, whereby an advantageous flow through for the individual cooling jackets and thus an advantageous cooling effect for the cylinder housing can be achieved.

It is also provided that the coolant inlet and the coolant outlet of the individual cooling jackets are arranged offset in the circumferential direction of the cylinder. Such an offset should at least affect the centers of the mouth cross-sections of the coolant inlets and the Relate coolant outlets. It can preferably be provided that the offset is 180 °. In this way, a flow of the same type as possible for the two sections of the individual cooling channels separated by the coolant inlets and the coolant outlets can be realized.

For such a cylinder housing according to the invention, it can then preferably be provided that the coolant inlet and the coolant outlet are arranged at the same height in relation to the longitudinal direction of the associated cylinder. The "same height" should relate at least to the mouth cross-sections as a whole and preferably to the centers of the mouth cross-sections.

A reciprocating piston device according to the invention, which can in particular be designed in the form of a (reciprocating piston) internal combustion engine, comprises at least one cylinder housing according to the invention and in each case one piston movably mounted in the cylinders of the cylinder housing.

By subdividing the cooling jackets assigned to the individual cylinders into a plurality of cooling channels, the (wall) surface that comes into contact with a coolant provided for flowing through the cooling jackets can be significantly increased compared to conventional cooling jackets, resulting in a correspondingly high heat transfer of the cylinder housing on the coolant can be achieved. As a result, it may be possible, if necessary, to have an overall reduced volume flow of the coolant circulate through the cooling jackets without reducing the cooling capacity. A reduced volume flow of the coolant can thus lead to a reduced delivery rate for a working machine provided for delivering the coolant (pump with a preferred use of a cooling liquid or compressor with a likewise conceivable use of a cooling gas as a coolant), which has a positive effect on both costs and costs the weight of the work machine and thus a reciprocating piston device comprising such a work machine can affect. The same applies to an internal combustion engine according to the invention comprising such a reciprocating piston device. If, as usual, in such an internal combustion engine, the working machine provided for delivering the coolant is driven by the internal combustion engine itself, the reduced delivery rate achievable according to the invention can lead to a reduction in fuel consumption. The relatively low volume flow of the coolant that can be achieved according to the invention can also have an indirect positive effect on the weight and also the dimensions of a cylinder housing according to the invention. This does not only apply because of a correspondingly reduced weight of the Coolant, which is particularly relevant in the case of the preferred use of a cooling liquid, but also because of the reduced structural weakening of the cylinder housing compared to a conventional cooling jacket that is not divided into a plurality of relatively small cooling channels due to the overall smaller cooling jacket and the stabilizing partition walls, which therefore also has to be compensated to a lesser extent by structural reinforcement measures.

In order to optimally utilize the advantage attainable by this embodiment of a cylinder housing according to the invention, it should preferably be provided that the flow cross-sections of the cooling channels (which are radially aligned with respect to a longitudinal axis of the respective cylinder) are designed as small as possible. In particular, it can be provided that the flow cross-section of at least one, individual or preferably all cooling channels is smaller than the (respectively smallest) opening cross-sections of both the coolant inlet and the coolant outlet. If the flow cross-section of one or more of the cooling channels varies along its course, this should apply to (in each case) the largest flow cross-section. However, too small a dimensioning of the flow cross-sections of the cooling channels should be avoided because this can have a negative effect on increasing the flow resistance for the coolant, which at least compensates or overcompensates for the achievable advantage of a comparatively low flow rate for the coolant. It should therefore preferably be provided that the (smallest) flow cross-section of the cooling channels is 4 mm ² . This can particularly preferably be between 4 mm ² and 100 mm ² , in particular between 4 mm ² and 25 mm ² .

A production of a cylinder housing according to the invention, but at least the section thereof comprising the cooling channels, can advantageously be lost (ie not) by means of a generative manufacturing method or by casting using at least one of the cooling jackets and preferably also the coolant inlet (s) and the coolant outlet (s) reusable) core take place because these manufacturing processes advantageously allow the integration of at least partially fully closed and thus not externally accessible cavities in a cylinder housing to be produced.

In such a production of a cylinder housing according to the invention or at least the section thereof comprising the cooling channels by means of casting using a lost core, it can preferably be provided that a soluble and in particular water-soluble base material, for example a salt, is used for the lost core because this enables a substantially complete flushing of the base material after the manufacture of the cylinder housing from the cavities provided as cooling channels and possibly also as coolant inlet and coolant outlet in a relatively simple manner. This applies in particular in comparison to a non-soluble base material, such as sand, which is regularly used for casting metal structures and which can be rinsed out, but does not dissolve in the rinsing liquid.

A casting core according to the invention, which is intended for use in a method according to the invention for producing a cylinder housing according to the invention, comprises at least a plurality of ring sections which are provided in groups in each case to form a cooling channel of one of the cooling jackets of the cylinder housing, with radially adjacent ring sections, the different of the Groups are assigned, merge into one another in a circumferential section and are thereby formed integrally. Such a casting core also has an inlet section provided for forming a coolant inlet of each cooling jacket of the cylinder housing and an outlet section provided for forming a coolant outlet for each cooling jacket of the cylinder housing, the connection sections being arranged offset in the circumferential direction of the ring sections of the respective cooling jacket.

A casting core according to the invention can advantageously be produced by means of casting, in which case a sand mold can advantageously be used for this purpose. This applies in particular if a soluble base material, and in particular a salt, is to be used as the base material for the design of the casting core.

According to an advantageous further development of a cylinder housing according to the invention, it can be provided that the opening cross section (s) of the coolant inlet / coolant inlets and / or the coolant outlet / coolant outlets over the entire length (in each case based on the longitudinal extent of the associated cylinder) of the Cooling jacket extends / extend so that the one or more coolant inlets and / or the one or more coolant outlets (each) open into each cooling channel of the cooling jacket assigned to them. This can ensure that the cooling liquid is distributed as evenly as possible to all of the cooling channels, which in turn can have an advantageous effect with regard to the flow through the cooling channels and thus with regard to the cooling effect for such a cylinder housing.

In a preferred embodiment of a cylinder housing according to the invention, it can also be provided that the cooling jackets are only provided in sections along the longitudinal extensions of the cylinders, ie in one or more sections of the individual cylinders, or the cooling ducts of the individual cooling jackets are designed to be non-uniform along the longitudinal extensions of the cylinders and / or are arranged. As a result, a non-uniform cooling effect can be realized along the longitudinal extent of the cylinder, which can be adapted as optimally as possible to the different heat transfer from the cylinders into the cylinder housing.

In an internal combustion engine according to the invention with such a cylinder housing, it can preferably be provided that the cooling channels are only provided in a section encompassing the top dead center of a cyclical movement of the associated piston, or the cooling channels are designed in such a way that the (average) cooling effect in the top dead center comprehensive third of the longitudinal extent of the cylinder is greater than in the middle third and / or the lower third. This ensures adequate cooling of the cylinder housing delimiting the cylinder in the upper third, in which the heat transfer is usually highest due to the primary combustion processes taking place there, while excessive cooling of the cylinder walls in the other sections is avoided. In this way, the optimum setting of the viscosity of a lubricant acting between the cylinder walls and the outer surfaces of the pistons can be achieved in these other sections with regard to a reduction in friction.

In a further preferred embodiment of a cylinder housing according to the invention it can be provided that at least some, preferably all of the adjacent cooling channels of a cooling jacket (and in particular all cooling jackets) are directly connected to one another by means of at least one and preferably by means of several connecting channels. These connecting channels can primarily serve to enable the formation of a sufficiently resilient casting core for the production of a cylinder housing according to the invention, which consequently has at least one, preferably several (for each pair of axially adjacent ring sections) connecting sections, the axially adjacent ring sections, which are used to form the cooling channels in the cylinder housing to be produced are provided, connect to one another. By means of the connecting sections, the ring sections, which are preferably relatively small in cross section and at the same time relatively long in the circumferential direction, can advantageously be supported against one another whereby a failure of the ring sections when casting a cylinder housing according to the invention using such a casting core can be avoided.

In a preferred development of such a cylinder housing according to the invention with connecting channels connecting the cooling channels to one another, at least some and preferably all of the connecting channels are designed to run obliquely with respect to the longitudinal axes of the associated cylinders. In the case of connecting channels running in a curved manner, the term "oblique" relates to the straight connecting line between the opening points of the individual connecting channels in the associated cooling channels. In this way, an arrangement, offset with respect to the circumferential direction, is achieved for the two opening points of the individual connecting channels, which can be connected with a pressure gradient, whereby a build-up of coolant within the connecting channels can be avoided or at least kept low. A casting core according to the invention for the design of such a cylinder housing is characterized in that the connection section or sections are oriented obliquely with respect to the (preferably coaxially oriented) central longitudinal axes of the ring sections.

In addition or as an alternative, other structural measures can also be provided for stabilizing a casting core according to the invention. For example, a support structure, for example made of metal wires, can be integrated into the core, this support structure remaining in a cylinder housing formed using such a casting core, i.e. being integrated into it.

If a sufficiently stable casting core can also be produced without connecting sections, these should not be provided if possible, in order to avoid a fluid-conducting connection between the cooling channels of the individual cooling jackets of the cylinder housing (with the exception of a possibly provided connection via the coolant inlets and the coolant outlets). This makes it possible to avoid flow losses which would occur when coolant flows over between the cooling channels via the connection sections, and a build-up of coolant within such connection channels.

The invention also relates to a motor vehicle, in particular a wheel-based motor vehicle (preferably a car or truck), with an internal combustion engine according to the invention. Here can the internal combustion engine can be provided in particular for (direct or indirect) provision of drive power for the motor vehicle.

The design of a cylinder housing according to the invention can serve not only to improve a (reciprocating) internal combustion engine but also to improve any reciprocating piston devices in which cooling is relevant through the active dissipation of thermal energy that passes from the cylinders into the respective cylinder housing. This can be the case with reciprocating compressors, for example.

The indefinite articles ("a", "an", "an" and "an"), in particular in the claims and in the description that generally explains the claims, are to be understood as such and not as numerals. Components specified in this way are therefore to be understood in such a way that they are present at least once and can be present several times.

Fig. 1:

einen Querschnitt durch eine Brennkraftmaschine mit einem erfindungsgemäßen Zylindergehäuse;

Fig. 2:

ein erfindungsgemäßes Zylindergehäuse, beispielsweise für eine Brennkraftmaschine gemäß der Fig. 1;

Fig. 3:

einen zur Herstellung eines Zylindergehäuses gemäß der Fig. 2 nutzbaren, erfindungsgemäßen Gießkern in einer perspektivischen Ansicht;

Fig. 4:

den Gießkern in einer Ansicht von oben;

Fig. 5:

den Gießkern in einer Ansicht von vorne; und

Fig. 6:

einen Abschnitt des Gießkerns in einer vergrößerten, perspektivischen Ansicht.

The present invention is explained in more detail below with reference to design examples shown in the drawings. The drawings show, in a partially simplified representation:

Fig. 1:

a cross section through an internal combustion engine with a cylinder housing according to the invention;

Fig. 2:

an inventive cylinder housing, for example for an internal combustion engine according to FIG Fig. 1 ;

Fig. 3:

one for producing a cylinder housing according to FIG Fig. 2 usable casting core according to the invention in a perspective view;

Fig. 4:

the casting core in a view from above;

Fig. 5:

the casting core in a view from the front; and

Fig. 6:

a portion of the casting core in an enlarged perspective view.

The Fig. 1 shows in a cross section an internal combustion engine (according to the invention) with a cylinder housing 10 according to the invention. This comprises a multi-part housing. In one First housing part of this housing, which is referred to below as cylinder housing 10 and which can preferably be made of metal and in particular a light metal, for example an aluminum alloy, a plurality of cylinders 12 arranged in series are formed. A piston 14 is movably guided within each cylinder 12. By means of a connecting rod 16, each of the pistons 14 is connected to a crank pin 18 of a crankshaft 20, which is rotatably mounted within a second housing part, which is referred to below as crankcase 22 and which connects to the underside of the cylinder housing 10. An oil pan 24 is integrated into the crankcase 22, in which a reservoir of (liquid) lubricant can be kept.

A movement of the pistons 14 along their longitudinal axes 26 or the longitudinal axes 26 of the associated cylinders 12 is translated into a rotary movement of the crankshaft 20 by means of the connecting rod 16 and by means of the bearings of the connecting rod 16, which are arranged decentrally with respect to the axis of rotation 28 of the crankshaft 20, on the associated crank pin 18 This coupling of the pistons 14 to the crankshaft 20 also ensures that the directions of movement of the pistons 14 always change when the associated crank pins 18 with their longitudinal or rotational axes 30 cross the longitudinal axes 32 of the associated cylinders 12 or pistons 14. The corresponding positions of the pistons 14 are indicated as top dead center (characterized by the greatest possible distance of the respective pistons 14 from the axis of rotation 28 of the crankshaft 20) and as bottom dead center (characterized by the position of the individual pistons as close as possible to that of the axis of rotation 28 of the crankshaft 20 Piston 14).

The pistons 14 can move through the targeted combustion of a fuel-fresh gas mixture in combustion chambers 32, each from the top of a piston 14, a section of the associated cylinder 12 and a cylinder head 34 that adjoins the upper end of the cylinder housing 10 , limited, can be effected. The initiation of such a combustion process takes place for each of the combustion chambers 32 in the (temporal) vicinity of the top dead center of the respective piston movement as a result of external ignition by means of spark plugs, not shown (if the internal combustion engine is designed as a gasoline engine) or by means of self-ignition as a result of, in particular, a relative high compression of the fuel-fresh gas mixture resulting in sufficient temperature increase (if the internal combustion engine is designed as a diesel engine). For this purpose, the fuel is introduced into the combustion chambers 32 in a controlled manner by means of inlet valves 38 via an injector 36 and the fresh gas, which can be exclusively or mainly air. That at The exhaust gas generated during the combustion of the fuel-fresh gas mixture is then discharged from the combustion chambers 32, controlled via outlet valves 40. The inlet valves 38 and the outlet valves 40 can be actuated in a known manner via one or more camshafts (not shown), which can be driven by the crankshaft 20, for example, via a so-called control drive.

A cooling jacket is provided for each of the cylinders 12 and consists of a plurality of closed, circumferential cooling channels 42 which are aligned parallel to one another and which are integrated in the cylinder housing 10. Furthermore, a coolant inlet 44 and a coolant outlet 46 are provided for each of the cooling jackets, these being arranged at the same height (based on the longitudinal extensions of the cylinder 12) and offset by 180 ° with respect to the longitudinal axis 26 of the respective cylinder 12 (diagonally opposite) . The coolant inlets 44 and the coolant outlets 46 open into all of the associated cooling channels 42.

The cooling jackets as well as the coolant inlets 44 and the coolant outlets 46 are part of a cooling system of the internal combustion engine, which also includes at least one coolant pump, which is used to pump a liquid coolant in a circuit, the coolant via the coolant inlets 44 into the respective associated cooling channels 42 flows and is discharged again from the cooling channels 42 via the respective associated coolant outlets 46. As it flows through the cooling channels 42, the coolant absorbs thermal energy, which first transfers from the combustion chambers 32 to the adjacent walls of the cylinder housing 10 and then to the coolant flowing in the cooling channels 42. This achieves the desired cooling of the combustion chambers 32 and the cylinder housing 10 of the internal combustion engine. The absorbed thermal energy is carried away from the coolant in an ambient heat exchanger (not shown) of the cooling system to a further cooling medium, in particular ambient air. The coolant can then be recirculated again into the cooling jackets of the cylinder housing 10 via the coolant inlets 44.

The cylinder housing in the Fig. 1 internal combustion engine shown as well as in the substantially identical cylinder housing 10 according to FIG Fig. 2 For example, the cooling jackets are each integrated into the cylinder housing 10 in only one section near the upper end of the cylinder 12, the longitudinal extent of these sections being, for example, approximately a quarter or a third of the total longitudinal extent of the cylinder 12. In the internal combustion engine according to Fig. 1 and at one Cylinder housing 10 according to the Fig. 2 Comprehensive internal combustion engine therefore direct cooling of the cylinder housing 10 takes place only in an area near the respective top dead center of the movements of the pistons 14. This is provided because there, when an internal combustion engine is operating, primarily thermal energy is generated, which is to be dissipated by the temperatures in the combustion chambers 32 and in the adjacent components limited to permissible values. In the remaining sections of the cylinders 12, however, the transfer of thermal energy from the cylinders 12 to the cylinder housing 10 and from there to the other parts of the internal combustion engine can be so small that direct cooling can be dispensed with. This can be the case, in particular, when the cylinder housing 10 is made from materials that conduct heat relatively well (for example aluminum alloys), so that the heat energy transferred can be dissipated sufficiently safely even without direct cooling. In any case, "overcooling" of these sections of the cylinder housing 10 can be avoided by such a configuration, which leads to a relatively high viscosity of the lubricant which is arranged between the outer surfaces of the piston 14 and the walls of the cylinder 12, and thus to a relatively high viscosity Could lead to frictional losses.

The production of a cylinder housing 10 according to the invention according to FIGS Fig. 1 and 2 can, for example, by casting using a casting core 48, as for example in the Figs. 3 to 5 is shown. This casting core 48, which can itself be formed, for example, by casting from a core material that includes, for example, salt as the base material, comprises a plurality of circular ring sections 50 that each serve to form a cooling channel of the cylinder housing 10 to be produced, with several (in the present case Embodiment four) groups are provided, each comprising a plurality of ring sections 50 which are arranged in coaxial alignment and axially spaced from one another. Each of these groups of ring sections 50 forms a cooling jacket assigned to a cylinder 12 of the cylinder housing 10 to be produced. The casting mold also forms two connection sections 52 for each of the groups of ring sections 50, which are arranged diagonally opposite one another with respect to the associated ring sections 50 and which merge into the associated ring sections 50. These connection sections 52 are provided to form a coolant inlet 44 and a coolant outlet 46 for the associated cooling jackets formed by the cooling channels 42.

As can be seen in particular from the Fig. 6 As a result, the ring sections 50 of adjacent groups, each lying at the same (axial) height, also merge into one another in one circumferential section, so that cooling channels 42 formed by the ring sections 50 a fluid-conducting connection with one another or an integral section which each belongs to two radially adjacent cooling channels 42 results. This configuration of the casting core 48 or the configuration of the cooling channels 42 achieved thereby enables the integration of cooling channels 42 of sufficiently large dimensions with regard to the flow cross-sections in relatively narrow separating webs 54 (cf. Fig. 2 ; eg approx. 8 mm wide in the narrowest section), which are each formed between adjacent cylinders 12 of the cylinder housing 10 according to the invention. Consequently, despite the relatively compact dimensions of the cylinder housing 10, which is made possible by the narrow dimensioning of the separating webs 54, a sufficient cooling capacity can also be achieved in the area of these separating webs 54.

In the casting core according to the Figs. 3 to 5 it is additionally provided that two axially spaced ring sections 50 are connected to one another by several (in the present embodiment four) connecting sections 56, whereby the stability of the casting core 48 in the areas of the ring sections 50 spaced apart from the connection sections 52 can be increased to prevent failure of the To avoid casting core 48 when casting a cylinder housing 10. These connecting sections 56 each lead to the formation of a connecting channel (not visible) which connects two axially spaced cooling channels 42 to one another in a fluid-conducting manner. Coolant can flow over between the cooling channels 42 via the connecting channels. In order to prevent coolant from building up in these connecting channels, they and thus also the connecting sections 56 of the casting core 48 are oriented obliquely or non-parallel with respect to the (coaxial) central longitudinal axes 58 of the cooling channels 42 or the ring sections 50. This results in different distances (with respect to the circumferential direction) to the associated coolant inlet 44 and to the associated coolant outlet 46 and, as a result, at least slightly different hydraulic pressures in these openings for the two openings of the connecting sections 56 into the cooling channels 42. This leads to pressure gradients over the connecting sections 56, as a result of which a flow through the connecting sections 56 is promoted.

REFERENCE LIST

10

Cylinder housing

12th

cylinder

14th

piston

16

Connecting rod

18th

Crank pin

20th

crankshaft

22nd

Crankcase

24

sump

26th

Longitudinal axis of the piston / cylinder

28

Axis of rotation of the crankshaft

30th

Longitudinal axis / axis of rotation of a crank pin

32

Combustion chamber

34

Cylinder head

36

Injector

38

Inlet valve

40

outlet valve

42

Cooling duct

44

Coolant inlet

46

Coolant outlet

48

Casting core

50

Ring section

52

Connection section

54

Divider

56

Connection section

58

Central longitudinal axis of a cooling channel / ring section

Claims (11)

1. Cylinder housing (10) for a reciprocating piston device, comprising at least two cylinders (12), each provided for receiving a piston (14) of the reciprocating piston device, and having for each of the cylinders (12) an integrated cooling jacket surrounding the circumference of the cylinders, wherein the cooling jackets are subdivided into a plurality of closed circulating cooling channels (42) and wherein a coolant inlet (44) opens into at least one of the cooling jackets and a cooling outlet (46) enters into at least one of the cooling jackets, wherein, of the cooling channels (42), those that are associated with the different ones of the cylinder merge into one another between the cylinders (12),
   characterized in that a coolant inlet (44) and a coolant outlet (46) open into each of the cooling jackets, wherein the coolant inlet (44) and the coolant outlet (46) are arranged offset in the circumferential direction of the associated cylinder (12).
2. Cylinder housing (10) according to claim 1, characterized in that the coolant inlet (44) and the coolant outlet (46) are arranged at the same height in relation to the longitudinal direction of the associated cylinder.
3. Cylinder housing (10) according to claim 1 or 2, characterized in that the flow cross-section of at least one cooling channel (42) is smaller than the opening cross-sections of the coolant inlet (44) and of the coolant outlet (46).
4. Cylinder housing (10) according to one of the preceding claims, characterized in that the coolant inlet(s) (44) and/or the coolant outlet(s) (46) open into each cooling channel (42) of the cooling jacket assigned thereto.
5. Cylinder housing (10) according to one of the preceding claims, characterized in that the cooling jackets are provided along the longitudinal extensions of the cylinders (12) only in sections or the cooling channels (42) of the cooling jackets are designed and/or arranged non-uniformly along the longitudinal extensions of the cylinders (12).
6. Cylinder housing (10) according to one of the preceding claims, characterized in that adjacent cooling channels (42) of a cooling jacket are directly connected to one another by means of at least one connecting channel.
7. Cylinder housing (10) according to claim 6, characterized in that the connecting channel is formed obliquely with respect to the longitudinal axis (26) of the associated cylinder (12).
8. Method for producing a cylinder housing (10) according to one of the preceding claims, characterized by the formation by means of a generative manufacturing method or by casting using a lost casting core (48) which forms at least the cooling jackets.
9. Method according to claim 8, characterized by the use of a soluble base material for the casting core (48).
10. Casting core (48) for use in a method according to claim 8 or 9, characterized by

    - a plurality of annular sections (50) provided in groups each for forming a cooling channel (42) of one of the cooling jackets, wherein radially adjacent annular sections (50) associated with different ones of the groups merge into each other in a circumferential section, and

    - a connecting section (52) provided for forming a coolant inlet (44) of each cooling jacket and a connecting section (52) provided for forming a coolant outlet (46) of each cooling jacket, wherein the connecting sections (52) are arranged offset in the circumferential direction of the annular sections (50) of the respective cooling jacket.
11. Casting core according to claim 10, characterized by at least one connecting section (56) interconnecting axially adjacent annular sections (50).

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