SE1650072A1 - Cylinder liner for an internal combustion engine - Google Patents

Abstract

The invention relates to a cylinder liner for an internal combustion engine (2) adapted to be arranged in a cylinder block (8) of an internal combustion engine (2), such that the cylinder liner (10) together with a cylinder head (14) and a piston (12) associated with the cylinder liner (10) delimits a combustion chamber (16), wherein the cylinder liner (10) comprises a cylinder shaped liner wall (24) extending longitudinally from an upper end (26) to a lower end (28), and wherein the upper end (26) has an upper end surface (32) extending essentially perpendicularly to the longitudinal extension of the liner wall (24). The liner wall (24) comprises an elongated recess (30) for isolation of the liner wall (24), wherein the recess (30) extends longitudinally from the upper end surface (32) in a direction towards the lower end (28) of the liner wall (24). The invention also relates to an internal combustion engine (2) and a vehicle (1) comprising such an internal combustion engine (2).(Fig. 4)

Description

1 Cylinder liner for an internal combustion engine TECHNICAL FIELD The present invention relates to a cylinder liner for an internal combustion engine, an internalcombustion engine comprising the cylinder liner and a vehicle comprising the internal combustion engine.

BACKGROUND ART internal cornhiistiori engines, such as diesel engines or Otto engines, are used in several typesof applications and vehicles, for example, in heavy vehicles, such as trucl iioyver plants, such as electric poyyer plants including a diesel generator, and in locornotives.

An internal combustion engine typically cornprises an engine block with at least one cylinder.The cylinder may comprise a replaceahle cylinder liner or sleeve, A piston is arranged to rrioveinside the cylinder liner and it seals one end of the cylinder liner such that a combustioncliarriber is formed hetyyeeri the piston, the cylinder liner and a cylinder head arranged at thetop end of the cylinder liner. Fuel is injected into the corribiistiori chaniher and is yaporizetl,ignited and corribiistetl. The gas pressure ironi the corrihustiori exerts a lorce on the rsistonsuch that it nioyes. The reciprocating rnotion of the piston is then 'translated into a rotationalrnovenient of the crankshatt. The piston nioyes betyyeen a top dead centre and a hottoin deadcentre, where the top dead centre is nearest to the cylinder head and the bottom dead centreis the opposite position furthest avifay from the cylinder head. The combustion is performedwhen the piston is close to or at the top dead centre. As the piston is pushed towards thebottom dead centre by the combustion gases, the combustion gases expand and as a result, their ternperature and pressure decreasesi A cylinder liner in an internal combustion engine is oi course subject to very high ternperatures. The niore heat is l 2 crankshaft. it is therefore desirabie to achieve and maintairi as high ternperature as possihieand thus rnihimize heat iosses from the cornbustion charnher. in the prior art there aresolutions for nfiinirnizing the heat iosses from the cornhustion chamber. For exampie,tiociirnerit LJS5522371 A discioses a corribiriatioiw of a cylinder head and a liner made of asilictin riitricie rnateriai. The ciocurnerit discioses a piuraiity' of gaskets with low conductivityarranged between the iiner and outer tuhirig for increasing the therrnai efficiency' ciuringoperation. Other known soiutions irirtiude various seaiing rievices arrangerà betyveen thecviinder' iiner and the rtylinder ite-ad. There is, hotfvetfer, still a need to improve soiutions forniinimizing heat iosses from a cornhustion chamber. Especialiv there is a need for solutionsthat are simpie and improve the efficiency and the fuei consumption of the interna! cornhustiori engine.

SUMMARY OF THE INVENTION lt is an object of the present invention to improve the efficiency of an internal combustionengine and thus for example to decrease the fuel consumption of an internal combustionengine. More specifically, it is an object of the invention to reduce heat losses in a combustion engine.

Further, it is an object of the invention to provide a cylinder construction for an internal combustion engine, which increases the efficiency ofthe internal combustion engine. lt is a further object to provide a simple solution for minimizing heat losses from a combustion engine.

The objects above are achieved by a cylinder liner for an internal combustion engine definedin the appended claims. The cylinder liner is adapted to be arranged in a cylinder block of aninternal combustion engine, such that the cylinder liner together with a cylinder head and apiston associated with the cylinder liner delimits a combustion Chamber. The cylinder linercomprises a cylinder shaped liner wall extending longitudinally from an upper end to a lowerend. The upper end has an upper end surface extending essentially perpendicularly to the longitudinal extension of the liner wall. The liner wall comprises an elongated recess for 3isolation of the liner wall and the recess extends longitudinally from the upper end surface in a direction towards the lower end of the cylinder liner. lt has been found that the cylinder liner for an internal combustion engine according to thepresent invention that comprises an elongated recess for isolation of the liner wall reducesheat losses from the cylinder liner. Thereby the efficiency of an internal combustion engine isimproved. ln addition, for example fuel consumption of an internal combustion engine can be reduced.

The present invention also relates to an internal combustion engine which comprises acylinder block with at least one cylinder liner, at least one cylinder head and at least onepiston arranged inside the at least one cylinder liner, such that a combustion chamber isformed and delimited by the at least one cylinder head, the at least one cylinder liner and theat least one piston. The internal combustion engine comprises the cylinder as defined above.Thus, the cylinder liner is configured as described above. Further modifications of the cylinderliner within the scope of the appended claims are possible, as described below in the detailed description with reference to the appended drawings.

The present invention also relates to a motor vehicle comprising an internal combustionengine as defined above. As above, also the internal combustion engine may be modifiedwithin the scope of the appended claims in accordance with the detailed description below with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, drawings illustrating an example ofthepresent invention are provided. Further objects and advantages of the invention will bedescribed more closely below in the detailed description. ln the appended drawings: Fig. 1 schematically illustrates a vehicle according to an embodiment of the invention;Fig. 2 schematically illustrates an internal combustion engine according to an embodiment of the invention; 4 Fig. 3 schematically illustrates a vertical cross-section of a cylinder liner according to anembodiment of the invention; andFig. 4 schematically illustrates an enlarged section of the area A in Figure 3 according to an embodiment of the invention.

DETAILED DESCRIPTION The invention is now described with reference to the cylinder liner, internal combustionengine and vehicle as generally described above. The cylinder liner of the invention is suitablyadapted to be arranged inside a cylinder of a cylinder block. The cylinder liner is furtheradapted to receive a piston moving inside the cylinder liner. The cylinder liner is thus sealed atthe lower end by the piston and at the upper end by a cylinder head. A number of piston ringsof the piston ensure that combustion gases do not leak out from the cylinder liner. Thecylinder liner is adapted to be arranged such that the upper end surface ofthe liner wall facesthe cylinder head. A sealing device may be arranged between the cylinder head and thecylinder liner. The liner wall is suitably shaped as an essentially circular cylinder with a centre line in the longitudinal direction of the cylinder liner.

By providing the liner wall with an elongated recess, the rate of heat transfer through the linerwall may be decreased. The clurability of the cylinder' liner is greatly affecterl hy the highternperatures created in the combustion charnher. The ttyiinder block in which the cylinderliner is arranged therefore typicaliy cornprises a plurality of passages for a Cooling fluid inorder to cool the cylinder liner. Such Cooling passages rnay however affect the rate of heattransfer through the liner wall. The rnore heat is lrept in the cornhustion chanaber, the greaterwork on the crankshaft. lt is therefore desirable to rnalntain a high temperature as long aspossible and thus to ininintize heat losses from the combustion chantber. The rate of heattransfer through the liner wall depends, for example, on the difference in temperature onboth sides of the liner wall and the thickness of the liner wall and thus the distance the heatrnust he conducted. Cooling passages surrounding the liner' wall trvill typically cause a hightemperature tfifferehtïe. This is especially the case at the upper end of the ttyiinder liner vvherethe combustion is performed and where the ternperature and pressure thus is the highest.

The rate of heat transfer through the liner wall is thereby increased and the ternperature of 5 the gases in the coinhustion chamber is rapidiy decreased. When the temperature efthegases in the combustion chamber is decreased, the efficiency of the internal combustionengine is decreased and the fuel consumption is thus disadvaittageously affected. Byproviding an elongated recess at the upper end of the liner yvall, an isoiating gap is formed.Trierefore, the heat from the combustion Chamber will be conducted around the recess inorder to be transferred through the liner wall to the cooling passages on the other side of theliner wall. Thus, the distance the heat is conducted is thereby increased and the rate of heattransfer through the liner wall is decreased. ln this way, heat losses from the cylinder liner are minimized.

By the elongated recess is meant a recess, which is longer than its width. The longitudinalextension (length) of the recess is thus larger than the width of the recess and the recess istherefore long and narrow. The elongated recess may be a slit or slot in the liner wall. Thelongitudinal extension of the recess may be also defined as the depth ofthe recess. Forclarification, the cross-section of the recess extends longitudinally from the upper end surfacein a direction towards the lower end of the cylinder liner. The cross-section ofthe recess isthereby elongated. The recess extends from the upper end surface and thus has an opening inthe upper end surface. The recess is suitably formed within the liner wall such that the recess is enclosed within the liner wall along the longitudinal extension of the recess.

The liner wall suitably comprises an inner side and an outer side. The inner side is adapted toconstitute the inner wall of the combustion chamber and thus faces the centre line ofthecylinder liner. The outer side may be partly surrounded by cooling recesses formed within the cylinder block in which the cylinder liner is adapted to be arranged.

According to an aspect ofthe invention, the recess accommodates an insulating medium, suchas a fluid including gas and/or liquid, vacuum or solid body. The recess may accommodate airand thus forms an air pocket inside the liner wall. Air that is essentially still constitutes a goodisolator and will therefore cause the heat to be conducted around the recess in order to betransferred through the liner wall. lf the recess is too wide, convection will cause air withdifferent temperatures to start flowing inside the recess. Flowing air is not as good isolator as still air. ln order to function as a good isolator the width of the recess is therefore suitably such 6 that air inside the recess is maintained essentially still. Alternatively, the recess accommodatesany other suitable fluid, i.e. gas and/or liquid, which will impair the heat transfer through theliner wall. The recess may accommodate a solid body of a material, which has a low thermalconductivity. ln addition, vacuum could be created in the recess. The recess is sealed air tightlyby means of a cylinder head, whereby a different gas composition than the ambient air, fluid or vacuum can be maintained within the recess.

According to an aspect of the invention, the recess extends at least partly along thecircumference ofthe cylinder liner. A plurality of elongated recesses may thereby be providedin the liner wall, intermittently or symmetrically along the circumference of the cylinder liner.The recess may alternatively extend along the whole circumference of the cylinder liner. lnthis way, the recess minimizes the heat transfer through the liner wall along the whole circumference ofthe cylinder liner.

According to an aspect ofthe invention, the recess has a width between 0.2-3 millimetres,preferably between 0.3-2 millimetres. By configuring the recess with such a width, an isolatingeffect is achieved while it can be ensured that a desired structural strength ofthe cylinder liner is achieved.

According to a further aspect of the invention, the longitudinal extension of the recess isadapted to substantially correspond to the distance between a top surface and an upperpiston ring of a piston associated with the cylinder liner when the piston is close to or at a topdead centre. The longitudinal extension of the recess thus suitably depends on theconfiguration of the piston associated with the cylinder liner. During operation, a piston movesinside the cylinder liner, wherein the reciprocating motion of the piston results in a rotationalmovement of the crankshaft. Combustion is performed when the piston is close to or at theupper end of the cylinder liner. During combustion, the piston may be positioned around 1millimetre from the cylinder head. At this stage, combustion gases with a very hightemperature may fill the small space between the piston and the cylinder liner down to anupper piston ring. The piston ring seals against the inner side ofthe cylinder liner. The areabetween the top surface of the piston and the upper piston ring is thus the area affected by the combustion gases with the highest temperature. The area of the liner wall corresponding 7 to the distance between the top surface of the piston and the upper piston ring, when thepiston is close to or at the top dead centre, is thus the area where the most heat |osses occur.By configuring the elongated recess such that the length of the recess is substantially as longas the distance between the top surface and the upper piston ring of the piston, it can beensured that the area where most heat |osses occur is isolated. ln this way, the heat |ossesfrom the cylinder liner can be minimized. The recess may extend longitudinally beyond thelevel of the upper piston ring of the piston associated with the cylinder liner, when the piston is in the top dead centre.

The cylinder liner suitably comprises an outer recess in the outer side of the liner wall. Theouter recess suitably extends circumferentially around the liner wall. The outer recess issuitably adapted to accommodate a sealing device, such as a sealing ring. ln this way, leakagefrom a cooling passage arranged adjacent the upper end of the cylinder liner can be prevented. The elongated recess suitably extends longitudinally beyond the outer recess.

According to an aspect ofthe invention, the longitudinal extension of the recess is at least 10millimetres, suitably 10-30 millimetres. ln this way, it is ensured that the extra distance for thecombustion gases to be conducted through the liner wall is sufficient to decrease the rate of heat transfer through the liner wall as desired.

According to a further aspect of the invention, the recess is inclined relative to the longitudinalextension ofthe liner wall. The recess may thus extend with an angle smaller or greater than90 degrees in relation to the upper end surface. The recess is suitably inclined in a directiontowards the inner side of the liner wall, and the angle is suitably from 70 to 89 degrees. Thethickness of the liner wall may vary along the longitudinal extension of the liner wall. lt is thusessential that the recess be provided such that the thickness ofthe liner wall surrounding therecess on both sides is sufficient to provide the desired strength. lt may therefore be desirableto incline the recess in relation to the longitudinal extension ofthe liner wall. Alternatively, the recess extends essentially perpendicularly to the upper end surface of the liner wall.

According to a further aspect of the invention, an annular protruding portion is arranged at the upper end surface of the cylinder liner. The annular protruding portion is suitably adapted 8 to correspond to an annular recess in the cylinder head. A sealing device may be arrangedbetween the cylinder liner and the cylinder head. The sealing device will thereby be clampedbetween the cylinder head and the cylinder liner and the protruding portion of the cylinderliner together with the recess ofthe cylinder head will create a tight sealing. The recesstherefore suitably extends from the annular protruding portion. Since the sealing device isclamped between the protruding portion of the cylinder liner and the cylinder head, thecombustion gases from the combustion chamber are prevented from leaking into the recess and the isolating effect of the recess can be further ensured.

According to an aspect, an internal combustion engine is provided. The internal combustionengine comprises a cylinder block with at least one cylinder liner, at least one cylinder headand at least one piston arranged inside the at least one cylinder liner, such that a combustionchamber is formed and delimited by the at least one cylinder head, the at least one cylinderliner and the at least one piston, wherein the cylinder liner is configured as described herein.The elongated recess at the upper end of the liner wall is suitably adapted to substantiallycorrespond to the distance between a top surface of the piston and an upper piston ring of the piston when the piston is close to or at the top dead centre.

The invention will now be further described with reference to the appended drawings.

Figure 1 schematicaliy shows a side view of a vehicle 1 according to an embodiment of theinvention. The vehicle 1 cornprises an internal coinhiistiori engine 2 connected to a gearbox fi.The gearbtax 4 is also connected to the driving witeeis li of the vehicle 1 through an outpiitsliaft of the gearbox (riot shown). The vehicle 1 may be a heavy vehicle, e.g. a truck or a bus.

The vehicle 1 may alternatively be a passenger car.

Figure 2 schematicaliy shows an internal combustion engine 2 according to an embodiment ofthe present invention. The internal combustion engine 2 is suitably arranged in a vehicleaccording to Figure 1. The internal combustion engine 2 comprises a cylinder block 8 with atleast one cylinder liner 10, at least one piston 12 and at least one cylinder head 14. Acombustion chamber 16 is delimited by the cylinder liner 10, the cylinder head 14 and the piston 12. The cylinder liner 10 is suitably removably arranged in the cylinder block 8 such that 9 it may be replaced. The piston 12 is movably arranged within the cylinder liner 10 forperforming strokes. The piston 12 is connected to a crankshaft 18 via a connecting rod 19 suchthat the reciprocating motion of the piston results in a rotational motion ofthe crankshaft 18.The crankshaft 18 is connected to a flywheel 20, which may be arranged in connection with agearbox 4 such that torque may be transferred to driving wheels of a vehicle 1. The cylinderhead 14 may comprise for example fuel injectors 22 for injecting fuel into the cylinder liner 10for combustion, inlet and exhaust ducts (not shown), cooling ducts (not shown) and inlet andexhaust valves (not shown). The cylinder liner 10 comprises a cylinder shaped liner wall 24 with an upper end 26 and a lower end 28.

The internal combustion engine 2 may be adapted to provide a four-stroke cycle. A strokerefers to the full travel of the piston 12 along the longitudinal extension of the cylinder liner10, in either direction. For a complete four-stroke cycle, the crankshaft 18 will turn tworevolutions. The position of the piston 12 closest to the cylinder head 14 is known as the topdead centre TDC and the position of the piston 12 farthest away from the cylinder head 14 isknown as the bottom dead centre BDC. A four-stroke cycle comprises a first stroke (intake)which begins with the piston at the top dead centre TDC and intake valves are open. When thepiston moves towards the bottom dead centre BDC, the volume ofthe combustion chamber16 increases and air or air-fuel mixture enters the combustion chamber. During the secondstroke (compression), the inlet and the exhaust valves are closed and the air or the air-fuelmixture in the combustion chamber is compressed as the piston 12 moves towards the topdead centre TDC. Just before the piston 12 reaches the top dead centre, TDC ignition begins.The pressure ofthe combustion gases pushes the piston 12 towards the bottom dead centreBDC in the third stroke (combustion), wherein mechanical work is produced. As the piston 12moves towards the bottom dead centre BDC the combustion gases expand and the pressureand the temperature of the combustion gases is thereby decreased. During the fourth stroke(exhaust), the exhaust valve is open and the combustion gas is thereby expelled when thepiston 12 moves towards the top dead centre TDC. At the end of the fourth stroke the exhaustvalve closes, the intake valve opens and the sequence may thereby be repeated in the next cycle.

The clurability of the cylinder liner 10 is greatly affectecl hy the high ternperatures created inthe cornbustion chamber 16 and the cylinder block 8 in which the cylinder liner 10 is arrangedtypically comprises a plurality of cooling passages (not shown) for a cooling fluid. Such coolingpassages may however increase the heat losses from the cylinder liner 10. The more heat thatis kept in the combustion chamber 16 the greater the work on the crankshaft 20 is. lt istherefore desirable to maintain a high temperature as long as possible and thus to minimizethe heat losses from the combustion chamber 16. The cylinder liner 10 according to theinvention therefore comprises an elongated recess 30 for isolation of the liner wall 24. The cylinder liner 10 is further described in relation to Figure 3.

Figure 3 schematically illustrates a vertical cross-section of a cylinder liner 10 for an internalcombustion engine 2 according to an embodiment of the invention. The cylinder liner 10 isarranged in a cylinder block 8 of an internal combustion engine 2 according to Figure 2. Thecylinder liner 10 comprises a cylinder shaped liner wall 24 with an upper end 26 and a lowerend 28, wherein the liner wall 24 extends longitudinally between the upper end 26 and thelower end 28. The upper end 26 has an upper end surface 32 extending essentiallyperpendicularly to the longitudinal extension ofthe liner wall 24. The upper end surface 32 isthus adapted to face a cylinder head 14. The liner wall 24 comprises an elongated recess 30for isolation of the liner wall 24, wherein the recess 30 extends longitudinally from the upperend surface 32 in a direction towards the lower end 28 of the liner wall 24. The cylinder head14 is herein illustrated comprising fuel injectors 22 for injecting fuel into the combustion chamber 16, an inlet valve 42 and an exhaust valve 44.

As rsreviously described, the durability of the cylinder liner 10 is greatly' affectetl by the highternperatures created in the combustion chamber 16 and the cylinder block 8 in which thecylinder' liner 10 is arranged 'therefore comprises a plurality of cooling passages 40 in order tocool the cylinder liner 10. Such cooling passages 40 inay however increase the rate of heattransfer through the liner wall 24. The rate of heat transfer through the liner »vall 24 dependsfor example on the difference in temperature on both sides ofthe liner wall 24 and thedistance the heat must be conducted. The coolirig passages 40 surrounding the liner wall 24 atthe upper end 26 where the teirlperature of the colnbustiorl gases is the highest will result in a lligh telnperature difference. The rate of lleat transfer through the liner ytfall 24 is thereby 11 increased and the temperature of the gases in the contbustioit chamber 16 is rapidiydecreased. Vtfhen the temperature ofthe gases in the combustion chamber 16 is decreased,the efficiency of the internal combustion engine 2 is decreased and the fuei consumption isthus impaired. By pretficïiiitg an eiengated recess 30 in the upper end 26 ef the liner waii 24 anisoiatirig gap is forrned and the heat from the combustion Chamber 16 must be conductedaround the recess 30 in order to be transferred through the liner wall 24 to the coolingpassages 40 on the other side of the liner wall 24. The distance the heat must be conducted isthereby increased and the rate of heat transfer through the liner wall 24 is reduced. ln this way, the heat losses from the cylinder liner 10 can be minimized.

The liner wall 24 comprises an inner side 46 and an outer side 48. The inner side 46 is insidethe combustion chamber 16 and thus faces the centre line C of the cylinder liner 10. The outerside 48 is partly surrounded by cooling recesses 40 in the cylinder block 8 in which the cylinderliner 10 is adapted to be arranged. The cylinder liner 10 suitably comprises an outer recess 50in the outer side 48 of the liner wall 24. The outer recess 50 suitably extends circumferentiallyaround the outer side 48 of the liner wall 24. The outer recess 50 is suitably adapted toaccommodate a sealing device (not shown), such as a sealing ring. ln this way, leakage fromthe cooling passage 40 arranged adjacent the upper end 26 of the cylinder liner 10 can be prevented.

The recess 30 suitably extends at least partly along the circumference of the cylinder liner 10.A plurality of elongated recesses 30 may thereby be provided in the liner wall 24,intermittently or symmetrically along the circumference ofthe cylinder liner 10. The recess 30may alternatively extend along the whole circumference ofthe cylinder liner 10. ln this way,the recess 30 can minimize the rate of heat transfer through the liner wall 24 along the whole circumference ofthe cylinder liner 10.

The recess 30 suitably accommodates an insulating medium, such as a fluid, i.e. a gas and/orliquid, vacuum or solid body. The recess 30 may accommodate air and thus forms an airpocket within the liner wall 24. Air that is essentially still constitutes a good isolator and willthus cause the heat to go around the recess 30 in order to pass through the liner wall 24. lf the recess 30 is too wide convection will cause air with different temperatures to start flowing 12 inside the recess 30. Flowing air is not as good isolator as still air. ln order to function as agood isolator the width of the recess 30 is therefore suitably such that air inside the recess 30is maintained essentially still. Alternatively, the recess 30 accommodates any other suitablegas or fluid, which will impair the heat transfer through the liner wall 24. The recess 30 mayaccommodate a solid body of a material, which has a low thermal conductivity. Since therecess 30 is sealed fluid tightly by means ofthe cylinder head 14 at the upper end surface 32,different fluids, solid body or vacuum can be maintained within the recess 30. The elongatedrecess 30 is shown in more detail in Figure 4, which schematically illustrates an enlargedsection of the area A in Figure 3 according to an embodiment ofthe invention. The elongatedrecess 30 is by definition longer than wide. The longitudinal extension (length) L of the recess30 is thus larger than the width W of the recess 30 and the recess 30 is long and narrow. Theelongated recess 30 may thus be a slit or slot in the liner wall 24. The longitudinal extension Lof the recess 30 may also be defined as the depth of the recess 30. The recess 30 extends fromthe upper end surface 32 and thus has an opening 60 in the upper end surface 32. The longitudinal extension L ofthe recess 30 is enclosed within the liner wall 24.

The width W of the recess 30 may be between 0.2-3 millimetres, preferably between 0.3-2millimetres. By configuring the recess 30 with a very small width W compared to the length agood isolating effect is achieved while ensuring a desired structural strength of the cylinder liner 10.

The longitudinal extension L ofthe recess 30 may be adapted to substantially correspond tothe distance between a top surface 70 and an upper piston ring 72 of a piston 12 associatedwith the cylinder liner 10, when the piston is close to or at a top dead centre. The longitudinalextension L of the recess 30 thus suitably depends on the configuration of the piston 12associated with the cylinder liner 10. The recess 30 of the cylinder liner 10 may extendlongitudinally beyond the level of the upper piston ring 72 ofthe piston 12 associated with thecylinder liner 10, when the piston 12 is in the top dead centre TDC. The recess 30 suitablycomprises a bottom 74. The longitudinal extension L of the recess 30 is thus suitably such thatthe bottom 74 of the recess 30 is closer to the lower end 28 ofthe cylinder liner 10 than theupper piston ring 72 of the piston 12 associated with the cylinder liner 10. Combustion is performed when the piston 12 is close to or at the top dead centre TDC at the upper end 26 of 13 the cylinder liner 10. During combustion, the piston 12 may be positioned for example around1 millimetre from the cylinder head 14. At this stage, combustion gas with a very hightemperature may fill the small space between the piston 12 and the liner wall 24 down to theupper piston ring 72. The piston ring 72 is sealing against the inner side 46 of the liner wall 24.The area between the top surface 70 of the piston 12 and the upper piston ring 72 is thus thearea affected by the combustion gas with the highest temperature. The area of the liner wall24 corresponding to the distance between the top surface 70 of the piston 12 and the upperpiston ring 72, when the piston 12 is at the top dead centre TDC, is thus the area where themost heat loss occurs. By configuring the elongated recess 30 such that the length L of therecess 30 is substantially as long as the distance between the top surface 70 and the upperpiston ring 72 of the piston 12, it can be ensured that the area where most heat loss occurs is isolated. ln this way, heat losses from the cylinder liner 10 can be minimized.

The longitudinal extension L ofthe recess 30 is at least 10 millimetres, suitably 10-30millimetres. This ensures that the extra distance for the combustion gas to be conductedthrough the liner wall 24 is sufficient to reduce the rate of heat transfer through the liner wall 24 as desired.

The recess 30 may be inclined relative to the longitudinal extension of the liner wall 24. Therecess 30 may thus extend with an angle oL smaller or greater than 90 degrees in relation tothe upper end surface 32. The recess 30 is suitably inclined in direction towards the inner side46 of the liner wall 24, and the angle is suitably from 70 to 89 degrees. The thickness of theliner wall 24 varies along the longitudinal extension of the liner wall 24. lt is thus essential thatthe recess 30 is provided such that the thickness ofthe liner wall 24 surrounding the recess 30on both sides is enough to provide the desired strength. lt may therefore be desirable toincline the recess 30 in relation to the longitudinal extension of the liner wall 24. Alternatively,the recess 30 extends essentially perpendicularly to the upper end surface 32 of the liner wall 24.

The liner wall 24 suitably comprises an annular protruding portion 76 at the upper end surface32 of the liner wall 24. The annular protruding portion 76 is suitably adapted to correspond to an annular recess 78 in the cylinder head 14. A sealing device 80 may be arranged between 14 the cylinder liner 10 and the cylinder head 14. The sealing device 80 will thereby be clampedbetween the cylinder head 14 and the cylinder liner 10 and the protruding portion 76 of thecylinder liner 10 together with the recess 78 of the cylinder head 14 will create a tight sealing.lt is therefore advantageous to provide the elongated recess 30 of the liner wall 24, such thatit extends from the annular protruding portion 76. The opening 60 of the recess 30 is thus inthe annular protruding portion 76. ln this way combustion gases from the combustionchamber 16 are prevented from leaking into the recess 30 and the isolating effect of therecess 30 is ensured. ln order to obtain optimal strength, the recess 30 is inclined towards theinner side 46 of the liner wall 24 with and angle oL smaller than 90 degrees, suitably from 70 to89 degrees, in relation to the upper end surface 32. ln this way, even though the outer recess50 decreases the thickness of the liner wall 24, sufficient amount of material of the liner wall 24 surrounds the recess 30 on both sides. lt should be understood that the above description of embodiments has been made in orderto exemplify the invention, and that alternative solutions will be obvious for a person skilled inthe art, however without departing from the scope of the invention as defined in the appended claims supported by the description and the drawings.

Claims (1)

CLAll\/IS

1. A cylinder liner for an internal combustion engine (2) adapted to be arranged in a cylinder block (8) of an internal combustion engine (2), such that the cylinder liner (10)together with a cylinder head (14) and a piston (12) associated with the cylinder liner(10) delimits a combustion chamber (16), wherein the cylinder liner (10) comprises acylinder shaped liner wall (24) extending longitudinally from an upper end (26) to alower end (28), and wherein the upper end (26) has an upper end surface (32)extending essentially perpendicularly to the longitudinal extension of the liner wall(24), characterized in that the liner wall (24) comprises an elongated recess (30) forisolation of the liner wall (24), wherein the recess (30) extends longitudinally from the upper end surface (32) in a direction towards the lower end (28) ofthe liner wall (24). A cylinder liner according to claim 1, characterized in that the recess (30)accommodates an insulating medium, such as a fluid including gas and/or liquid, vacuum or a solid body. A cylinder liner according to claim 2, characterized in that the insulating medium is air. A cylinder liner according to any of the preceding claims, characterized in that the recess (30) extends at least partly along the circumference of the cylinder liner. A cylinder liner according to any of claims 1-3, characterized in that the recess (30) extends along the whole circumference ofthe cylinder liner. A cylinder liner according to any of the preceding claims, characterized in that the recess (30) has a width (W) between 0.3-2 millimetres. A cylinder liner according to any of the preceding claims, characterized in that thelongitudinal extension (L) of the recess (30) is adapted to substantially correspond tothe distance between a top surface (70) and an upper piston ring (72) of a piston (12) associated with the cylinder liner when the piston is close to or at a top dead centre. 8. 10. 11. 12. 13. 14. 16A cylinder liner according to any of the preceding claims, characterized in that thelongitudinal extension (L) of the recess (30) is at least 10 millimetres, suitably 10-30 mm. A cylinder liner according to any of the preceding claims, characterized in that therecess (30) is inclined relative to the direction of the longitudinal extension of the liner wall (24). A cylinder liner according to claim 9, characterized in that the recess (30) is inclined ina direction towards the inner side of the liner wall (24) and extends with an anglesmaller than 90 degrees, suitably from 70 to 89 degrees, in relation to the upper end surface. A cylinder liner according to any of the preceding claims, characterized in that anannular protruding portion (76) is arranged at the upper end surface (32) ofthe liner wall (24) and the recess (30) extends from of the annular protruding portion (76). An internal combustion engine, comprising a cylinder block (8) with at least onecylinder liner (10), at least one cylinder head (14) and at least one piston (12) arrangedinside the at least one cylinder liner (10), such that a combustion chamber (16) isformed and delimited by the at least one cylinder head (14), the at least one cylinderliner (10) and the at least one piston (12), characterized in that the cylinder liner (10) is configured as described in any of claims 1-11. An internal combustion engine according claim 12, characterized in that the elongatedrecess (30) in the liner wall (24) of the cylinder liner (10) is adapted to substantiallycorrespond to the distance between a top surface (70) ofthe piston (12) and an upper piston ring (72) of the piston (12) when the piston is close to or at a top dead centre. A motor vehicle characterized in that it comprises an internal combustion engine (2) according to claim 12 or 13.