Gasket for cylinder liner and strongback

Abstract

The present invention pertains to a cylinder liner gasket for use in a combustion engine with a strongback as well as a corresponding cylinder head assembly and method for assembling the cylinder liner with a gasket. In particular, the cylinder liner gasket may effectively provide an improved sealing without introducing excessive wear of the cylinder liner and an adjacent strongback. Accordingly, a cylinder head assembly (10) for a combustion engine is suggested, comprising a cylinder head (12), a cylinder liner (14), and a strongback (16) configured for attachment to the cylinder head (12) and for accommodating the cylinder liner (14) in the assembled state. An upper flange portion (18) of the cylinder liner (14) is arranged between the cylinder head (12) and a portion of a top surface of the strongback (16) facing the cylinder head (12) in the assembled state, wherein a cylinder liner gasket (20) is arranged at least between a portion of the bottom surface of the flange portion (18) of the cylinder liner (14) and the top surface of the strongback (16).

Description

Technical Field

[0001] The present invention pertains to a cylinder liner gasket for use in a combustion engine with a strongback as well as a corresponding cylinder head assembly and method for assembling the cylinder liner with a gasket. In particular, the cylinder liner gasket may effectively provide an improved sealing without introducing excessive wear of the cylinder liner and an adjacent strongback.Technological Background

[0002] One of the functions of the strongback in a cylinder head assembly is to conform to any deformation of the cylinder liner so as to avoid a relative movement between both parts. In this manner, the occurrence of wear at the connecting interface between the strongback and the cylinder liner may be considerably reduced or avoided to the largest possible extent. In particular, for engines without such strongback, i.e. with a direct contact of the cylinder liner to the engine block, it has been found considerably challenging to address this issue based on the typically very stiff engine block, which hence cannot conform to any deformation of the cylinder liner. Thereby, relative movements and corresponding wear may occur, ultimately resulting in a potential leaking of coolant or cooling water out of the engine.

[0003] However, on the other side, the strongback should also be stiff enough to minimize the occurrence of deformations of the cylinder liner, which may have an adverse impact on the combustion. For example, fourth order deformations of the cylinder liner may have the effect that the piston rings within the cylinder liner no longer function as intended, if they exceed a predetermined determined limit.

[0004] Attempts to address these issues and to e.g. increase the stiffness and improve the distribution of the stiffness of the strongback, e.g. to avoid such deformations of the cylinder liner, include the use of different materials. One such example includes the change from gray cast iron to spheroidal graphite iron. However, it has been found that such material change may simultaneously have an adverse effect on the tribology properties of the two parts, i.e. the cylinder liner and the strongback, such that the wear between these parts may increase based on a sliding movement, even if the extent of movement is not increased compared with previously used materials.

[0005] Accordingly, a need exists to reduce the occurrence of wear of the cylinder liner and / or the strongback while enabling a sufficient sealing to avoid leakage of coolant or combustible fluids.Summary of the Invention

[0006] Starting from the prior art, it is an objective to provide a new and inventive connection between the cylinder liner and a strongback of a combustion engine. In particular, it may be an objective to provide a means to reduce the occurrence of leakage while providing a sufficient conformability with reduced wear between the strongback and the cylinder liner.

[0007] This objective is solved by means of a cylinder head assembly, a cylinder liner gasket, and a method according to the features of the independent claims. Preferred embodiments are set forth in the present specification, the Figures as well as the dependent claims.

[0008] Accordingly, a cylinder head assembly for a combustion engine is suggested, comprising a cylinder head, a cylinder liner, and a strongback configured for attachment to the cylinder head and for accommodating the cylinder liner in the assembled state. An upper flange portion of the cylinder liner is arranged between the cylinder head and a portion of a top surface of the strongback facing the cylinder head in the assembled state and a cylinder liner gasket is arranged at least between a portion of the bottom surface of the flange portion of the cylinder liner and the top surface of the strongback.

[0009] Furthermore, a cylinder liner gasket is suggested that is configured for arrangement between a portion of a bottom surface of a flange portion of a cylinder liner and a top surface of a strongback of a combustion engine, wherein the cylinder liner gasket comprises a varying thickness and / or material density in the circumferential and / or radial direction.

[0010] According to a further aspect, a method for assembling a cylinder liner to a strongback of a combustion engine is suggested, comprising the steps of: placing a cylinder liner gasket between a portion of a bottom surface of a flange portion of the cylinder liner and a top surface of the strongback; in the assembled state of the cylinder liner, mounting a cylinder head to the strongback so as to apply a screwing force to the cylinder liner gasket with a first predefined screwing force, thereby displacing at least a portion of the cylinder liner gasket; and mounting the cylinder head to the strongback by applying a second nominal screwing force being smaller than the first predefined screwing force.Brief Description of the Drawings

[0011] The present disclosure will be more readily appreciated by reference to the following detailed description when being considered in connection with the accompanying drawings in which: Fig. 1 shows a schematic longitudinal section of a cylinder head assembly according to a preferred embodiment of the invention; Fig. 2 shows a cylinder liner gasket according to the invention according to an embodiment; and Fig. 3 shows a cylinder liner gasket according to the invention according to another embodiment. Detailed Description of Preferred Embodiments

[0012] In the following, the invention will be explained in more detail with reference to the accompanying figures. In the Figures, like elements are denoted by identical reference numerals and repeated description thereof may be omitted in order to avoid redundancies.

[0013] In Figure 1 a schematic cylinder head assembly 10 is shown in a longitudinal section. The cylinder head assembly 10 may e.g. be mounted in an engine block of a combustion engine to form a respective cylinder thereof. Accordingly, the cylinder head assembly 10 comprises a cylinder head 12, which is depicted as a rectangular structure merely for improved intelligibility and overview of the relative arrangement of the components of the cylinder head assembly 10. The cylinder head 12 is mounted on top of a cylinder liner 14, which forms an inner liner within a bore of a strongback 16. Accordingly, the bore of the strongback 16 preferably accommodates or surrounds the cylinder liner 14 while at the same time ensuring that at least around a portion of the cylinder liner 14 a cavity is defined, which may be used for the circulation of a coolant.

[0014] A top portion of the cylinder liner 14 extends radially outward forming a flange portion 18, which is arranged between the bottom surface of the cylinder head 12 and the top surface of the strongback 16. In this manner, the flange portion 18 of the cylinder liner 14 is compressed between the cylinder head 12 and the strongback 16. In order to provide an improved sealing between the flange portion 18 and the strongback 16, a cylinder liner gasket 20 is arranged between the bottom surface of the flange portion 18 and the top surface of the strongback 16.

[0015] According to the present example, the cylinder liner gasket 20 comprises a portion having a varying thickness 22, as indicated by the corresponding height in the longitudinal section. The portion with the varying thickness 22 mag e.g. comprise an increased thickness in the radially inward direction of the cylinder liner gasket 20. It will be understood that such varying thickness is not limited to the step-wise variation in thickness, as depicted in Figure 1, but a more gradual variation may be present instead.

[0016] The varying thickness may be adapted to the presence of one or more local stresses, which may occur upon assembly, wherein screws 24 provide an engagement between the cylinder head 12 and the strongback 16. The screws 24 are depicted to be received within the strongback 16. In particular, not shown in further detail in Figure 1, the screws 24 may extend through the strongback 16 towards a crank case (not shown) for a screwing engagement with respective threads within the crank case. The screwing engagement may typically result in larger screwing or compressive forces around the respective screws 24 compared with portions of the cylinder liner 14 and / or strongback 16 not being directly adjacent to the screws 24. As a result, an uneven pressure distribution may be present, potentially causing a leakage from the cavity between the cylinder liner 14 and the strongback 16 and / or an increase in wear in case of relative movement.

[0017] The portion with the varying thickness 22, e.g. having at least partially a different thickness than an adjacent portion of the cylinder liner gasket 20, effectively counteracts such uneven pressure distribution by ensuring that a more even connection between the surfaces adjacent to the cylinder liner gasket 20 are provided. This is because e.g. an increased thickness for those portions of the cylinder liner 14 otherwise not providing a sufficient sealing causes an increase in the locally applied screwing force while a reduced thickness around the screws 24 enables that focal stresses may be levelled out more evenly.

[0018] In the present, non-limiting embodiment, a cylinder head gasket 26 is furthermore arranged between a bottom surface of the cylinder head 12 and a top surface of the flange portion 18 of the cylinder liner 14. Such cylinder head gasket 26 may also comprise a portion 28 with a varying thickness and / or material density and ensures that upon assembly and the application of a nominal screwing force a sealing between the cylinder head 12 and the cylinder liner 14 may be improved. Accordingly, the risk of combustible fluids inadvertently leaking via the interface between the cylinder head 12 and the flange portion 18 of the cylinder liner 14 may be considerably reduced. Furthermore, the risk of inadvertent deformations of the flange portion 18 of the cylinder liner 14 upon application of the nominal screwing force may be reduced.

[0019] For both the cylinder liner gasket 20 and the cylinder head gasket 26 the portion 22, 28 having a varying thickness and / or material density may be at least partially present upon initial assembly. Preferably, the portion 22, 28 is at least partially formed based on the application of an initial predefined screwing force being larger than a subsequently applied nominal screwing force. The application of such initial predefined screwing force may hence result in a biasing or displacement of at least a portion of the cylinder liner gasket 20 and cylinder head gasket 26. Thereby, not only a more even pressure distribution may be achieved. The cylinder liner gasket 20 and the cylinder head gasket 26 also provide a level of adaptation to manufacturing tolerances and local height differences of the interfacing surfaces of the cylinder head 12, the cylinder liner 14 or flange portion 18 thereof, and the strongback 16.

[0020] In Figure 2 an example of a cylinder liner gasket 20 is shown for a strongback 16 configured for attachment with a cylinder head 12 in a configuration with four screws. As shown, the cylinder liner gasket 20 is essentially ring-shaped and provides a structure surrounding a bore 30 of the strongback 16. Furthermore, the cylinder liner gasket 20 comprises a total of four portions 22 having a varying thickness and / or material density, which essentially correspond to a respective portion of the strongback 16 configured to receive a screw 24 for engagement with the cylinder head 12. Accordingly, these portions 22 may each extend about 30 degrees in the circumferential direction and are equally spaced apart from each other in conformity with the arrangement of the screws 24.

[0021] In the example according to Figure 2 the cylinder liner gasket 20 is configured to surround the respective screws 24 within respective recesses 32. Thereby, any inhomogeneous local stresses at the level of the screws 24 and directly adjacent thereto may be distributed more evenly.

[0022] An alternative example of a cylinder liner gasket 20 is depicted in Figure 3, wherein the cylinder liner gasket 20 is also arranged directly adjacent to bores or through-holes 34 of the strongback 16, but comprises the corresponding portions with a varying thickness and / or material density only at the radially inward side. In other words, the portions 22 may optionally directly abut the respective screws 25 in the assembled state, but do not surround or fully enclose the screws 24. Alternatively, the cylinder liner gasket 20 may also be formed and arranged so as to define a predefined spacing or small gap to the respective screws, which may depend on the effect of the application of the screwing force upon assembly, in particular an initial predefined screwing force applied to displace or bias a portion of the cylinder liner gasket 20.

[0023] It will be understood that the portions 22 may also be formed with recesses 32 having a C-shape or U-shape, such that the portions may at least partially surround the respective screws 24. Such a configuration may also be advantageous to facilitate and monitor the arrangement of the cylinder liner gasket 20 and its portions 22 relative to the respective bores or through-holes 34 of the strongback 16.

[0024] It will be obvious for a person skilled in the art that these embodiments and items only depict examples of a plurality of possibilities. Hence, the embodiments shown here should not be understood to form a limitation of these features and configurations. Any possible combination and configuration of the described features can be chosen according to the scope of the invention.

[0025] This is in particular the case with respect to the following optional features which may be combined with some or all embodiments, items and / or features mentioned before in any technically feasible combination.

[0026] A cylinder head assembly for a combustion engine is provided.

[0027] The cylinder head assembly comprises a cylinder head, a cylinder liner, and a strongback configured for attachment to the cylinder head and for accommodating the cylinder liner in the assembled state. An upper flange portion of the cylinder liner is arranged between the cylinder head and a portion of a top surface of the strongback facing the cylinder head in the assembled state and a cylinder liner gasket is arranged at least between a portion of the bottom surface of the flange portion of the cylinder liner and the top surface of the strongback.

[0028] According to the present invention it has been found that the placement of a cylinder liner gasket between the adjacent surfaces of the cylinder liner and the strongback enables that an improved pressure distribution of the connecting interface may be provided.

[0029] To further facilitate the improved pressure distribution of the connecting interface, the cylinder liner gasket preferably comprises a varying thickness and / or material density in the circumferential and / or radial direction. Based on the varying thickness and / or material density of the cylinder liner gasket, a pressure may be distributed in a more homogenous manner. This is because the varying thickness and / or material density of the cylinder liner gasket may compensate for any local pressure differences occurring during the screwing engagement of the cylinder head.

[0030] In other words, for positions on the cylinder liner surface and strongback surface that would typically be associated with a reduced local pressure the cylinder liner gasket may be adapted to locally provide e.g. a corresponding increased thickness, such that, in the assembled state under screwing engagement, e.g. provided by screws inserted in the cylinder head and extending through the strongback for a screwing engagement with respective threads in a crank case, a larger pressure may be present at such positions, thereby providing a more even pressure distribution. By the same token, the cylinder liner gasket may e.g. comprise a reduced thickness at portions corresponding to a typically increased local pressure to accordingly reduce the pressure.

[0031] By enabling the improved pressure distribution, the risk of occurring leakages may be effectively reduced, since a sufficient pressure may be ensured along the entire circumference of the cylinder liner gasket and hence between the cylinder liner and the strongback. For example, coolant or cooling water present in a cavity between the cylinder liner and the strongback is blocked from leaking out of said cavity due to advantageous configuration of the cylinder liner gasket.

[0032] Furthermore, the level of deformation of the cylinder liner that may occur when e.g. the cylinder head engages the strongback may be reduced based on the cylinder liner gasket, since focal pressures and corresponding biases, in particular of the flange portion of the cylinder liner, may be avoided or at least be more evenly distributed. Thereby, an improved interface may be maintained between the cylinder liner and the cylinder head, such that the risk of inadvertent leakage of a combustion fluid may be considerably reduced.

[0033] At the same time, any deformations occurring to cylinder liner may still be accommodated by the strongback, since based on the implementation of the cylinder liner gasket no adaptations are required to the structure and material of the strongback.

[0034] In the assembled state the cylinder liner is preferably accommodated or housed within a bore of the strongback, such that the strongback may surround the cylinder liner. The cylinder liner is preferably at least partially accommodated by means of an interference fit. The flange portion may accordingly extend over a top surface of the strongback and may be brought in a sandwiched construction between said surface of the strongback and an adjacent surface of the cylinder head at an opposing side of the flange portion.

[0035] The cylinder liner gasket is preferably formed as a ring-shaped element, such that a continuous structure is provided in the circumferential direction. Preferably, the cylinder liner gasket is exclusively arranged between a portion of the bottom surface of the flange portion of the cylinder liner and the top surface of the strongback, such that it is preferably designed to provide an adaptation only for any otherwise occurring pressure differences, yet does not inadvertently interfere with further parts or components.

[0036] Preferably, the strongback is configured receive a plurality of screws, wherein the cylinder liner gasket surrounds at least a portion of each of the screws or is arranged adjacent to a portion of each of the screws in the assembled state.

[0037] For example, the flange portion may be clamped between the strongback and the cylinder head, wherein a plurality of bores may be present in the flange portion to receive a corresponding number of screws. The screws may be received by corresponding through-holes in the strongback and may extend through the screwback to provide a screwing engagement with corresponding threads within a crank case.. The configuration of the cylinder liner gasket may accordingly comprise a corresponding number of recesses, which are C-shaped, U-shaped or be essentially formed as a through-hole to accordingly at least partially accommodate a corresponding screw.

[0038] Alternatively, the cylinder liner gasket may be formed and positioned to provide an abutment to each of the respective screws while essentially extending radially inward, forming a radial inner sealing without extending at least partially around each of the screws. The configuration may be based on the required pressure distribution.

[0039] In this regard, a portion of the cylinder liner gasket adjacent the screws preferably comprises a reduced thickness and / or an increased material density. For example, a reduced thickness around a least a portion of each screw may ensure that, upon screwing engagement and the application of a screwing and / or clamping force, a typically occurring locally increased pressure around the screw may be reduced while at the same time enabling that a force and corresponding pressure may be increased for portions of the cylinder liner and strongback that are not directly adjacent to the screws. Accordingly, the modification of the cylinder liner gasket around each of the screws provides an adaptation that may result in an improved pressure distribution and hence a more even sealing between the cylinder liner and the strongback.

[0040] By the same token, an increased material density may result from the application of a predefined screwing force causing a local material displacement and or plastic deformation within the portion of the cylinder liner gasket. The surface of the portion of the cylinder liner gasket may define a plane, e.g. with an inclination or declination, wherein the local material density may be adapted to the local focal pressure upon application of the screwing and / or clamping force. Portions with a lower material density may furthermore optionally define a less stiff portion with improved elasticity or resilience, which may further facilitate a more even pressure distribution.

[0041] Depending on the configuration of the cylinder head, the cylinder liner, and the strongback, multiple portions of the cylinder liner gasket may comprise a reduced thickness and / or an increased material density. In particular, each of said portions of the cylinder liner gasket may extend between 20 degrees and 50 degrees of the circumference of the cylinder liner gasket. Alternatively or in addition, said portions of the cylinder liner gasket may be equally spaced-apart from each other along the circumference of the cylinder liner gasket.

[0042] For example, the circumferential extension of each portion may correspond to a corresponding portion of the cylinder liner and / or strongback experiencing a larger pressure, such that the reduced thickness and / or increased material density may provide a reduced pressure and corresponding more even distribution along the circumferential direction. The thickness and / or material density may furthermore vary in the radial direction, such that e.g. stress focal points may be accordingly reduced in the radial direction and / or may be biased towards a radial inner potion for improved sealing. Preferably, the portions are not only equally spaced apart from each other, but also equally distributed relative to adjacent and / or interfacing the cylinder liner and strongback surfaces.

[0043] Preferably, each of said portions corresponds to a portion of the top surface of the strongback configured to receive a screw in the assembled state. For example, the cylinder head assembly may be mounted using four screws. Accordingly, the circumferential extension of each portion may comprise e.g. between 20 degrees and 40 degrees while the circumferential extension of the portions between the portions having a reduced thickness and / or increased material density may comprise e.g. between 50 degrees and 70 degrees. For assemblies requiring six screws or eight screws the extension of the former portions may be accordingly reduced.

[0044] As described above, the portions may advantageously comprise a corresponding recess, e.g. being C-shaped, U-shaped, or shaped as a through-hole to accommodate a respective screw. Preferably, the portion comprises an essentially symmetric shape.

[0045] Preferably, the cylinder liner gasket is formed of a metal or metal alloy. Such material may have the advantage that an improved adaptability and conformability to local pressures and / or sufficient plastic deformation upon the respective pressures received may be provided. A metal-based cylinder liner gasket may also provide improved robustness and / or resilience. The material may be chosen according to the required conformability and / or the operating conditions and configuration of the combustion engine.

[0046] In order to provide an improved fitting of the cylinder liner gasket that is adapted to the respective cylinder head assembly and which takes into account any manufacturing tolerances, the varying thickness and / or the varying material density of the cylinder liner gasket is preferably formed by the application of an initial screwing force for the screwing engagement that is larger than a subsequent application of a nominal screwing force in the assembled state.

[0047] Accordingly, a displacement of the material may be provided by the predefined initial screwing force, which may result e.g. in a reduced thickness around those areas being subjected to the largest screwing force or stress. In other words, the cylinder liner gasket may be formed by a material flow or displacement, wherein more material with a corresponding larger thickness may accumulate at those areas otherwise being subjected to a lower screwing force. Thereby, upon application of the nominal screwing force, a more even pressure distribution with a corresponding improved sealing may be provided.

[0048] The material of the cylinder liner gasket may furthermore be adapted to enable such material displacement and / or may be chosen to further optimize the tribology in view of the adjacent cylinder liner and strongback, e.g. to anticipate or alleviate wear based on any relative movement or sliding.

[0049] In this regard, the cylinder liner gasket may also be formed of materials having a different Young's modulus. Accordingly, different stiffness and resilience properties may be provided, which may not only be advantageous upon the application of an initial predefined screwing force, but independently also to distribute stresses and pressures more evenly in the assembled state of the cylinder liner gasket and the cylinder head assembly as a whole.

[0050] To further improve the pressure distribution, also between the cylinder liner and the cylinder head, the cylinder head assembly may further comprise a cylinder head gasket being arranged at least between a top surface of a portion of the flange portion of the cylinder liner and a bottom surface of the cylinder head, wherein the cylinder head gasket comprises a varying thickness in the circumferential and / or radial direction.

[0051] Similar to the cylinder liner gasket described above, such local differences in thickness and / or material density advantageously effectively counteract any inhomogeneous pressure distributions between the cylinder head and the cylinder liner. Accordingly, a more even pressure distribution may be provided, resulting in an improved sealing while avoiding or at least reducing the occurrence of any inadvertent deformations of the cylinder liner, in particular its flange portion, upon application of a required screwing force. By means of the improved sealing the risk of leakage of combustible fluids via the interface between the cylinder head and the cylinder liner may be considerably reduced.

[0052] The implementation of both the cylinder liner gasket and the cylinder head gasket has furthermore been found to be synergistic in providing an improved pressure distribution in the two connections between the cylinder liner and the strongback and the cylinder liner and the cylinder head, potentially resulting in an even lower deformation of the cylinder liner and further wear reduction.

[0053] According to a further aspect, a cylinder liner gasket is provided, preferably a metal cylinder liner gasket.

[0054] The cylinder liner gasket is configured for arrangement between a portion of a bottom surface of a flange portion of a cylinder liner and a top surface of a strongback of a combustion engine, wherein the cylinder liner gasket comprises a varying thickness and / or material density in the circumferential and / or radial direction.

[0055] As described above, the cylinder liner gasket may advantageously improve a pressure distribution between the cylinder liner and the strongback. In this regard, the varying thickness and / or material density may compensate for any focal stresses caused by locally increased screwing forces, in particular around or at screws in case of a screwing engagement of a cylinder head and a strongback. The varying thickness, for example, may be present prior to the application of an initial predefined screwing force, wherein the screwing force may bias a portion of the material of the cylinder liner gasket, resulting e.g. in a modified thickness distribution of the cylinder liner gasket. In such manner, a connection or contact between the cylinder liner and the strongback for adjacent portions of the cylinder liner gasket may be improved, thereby providing a more homogeneous pressure distribution.

[0056] Alternatively, the cylinder liner gasket may also be formed as an essentially plane surface having an essentially homogeneous thickness prior to the application of an initial screwing force, wherein a thickness around or at the screws may be reduced upon the application of said screwing force, for example by plastic deformation, hence resulting in the varying thickness and / or material density.

[0057] Accordingly, portions of the cylinder liner gasket are preferably configured to be displaced in a predefined direction upon application of a predefined compression force. This predefined direction may particularly correspond to a direction away from a corresponding edge or recess configured to be adjacent to a screw upon assembly of a cylinder head assembly, such that the local stress around each of such screws may be effectively reduced and an improved pressure may be established at those portions of the cylinder liner gasket not being adjacent to the respective screw.

[0058] Each of said portions may extend between 20 degrees and 50 degrees of the circumference of the cylinder liner gasket and / or said portions may be equally spaced-apart from each other along the circumference of the cylinder liner gasket.

[0059] As described above, the circumferential extension of each portion may correspond to a corresponding portion of the cylinder liner and / or strongback experiencing a larger pressure, such that the reduced thickness and / or increased material density may provide a reduced pressure and corresponding more even distribution along the circumferential direction. Preferably, the portions are not only equally spaced apart from each other, but also equally distributed relative to adjacent and / or interfacing the cylinder liner and strongback surfaces. For example, each of said portions may correspond to a portion of the top surface of the strongback configured to receive a screw in the assembled state, such that for a cylinder head assembly to be mounted using four screws the circumferential extension of each portion may comprise e.g. between 20 degrees and 40 degrees while the circumferential extension of the portions between the portions having a reduced thickness and / or increased material density may comprise e.g. between 50 degrees and 70 degrees. Furthermore, each of said portions may comprise a corresponding recess, e.g. being C-shaped, U-shaped, or shaped as a through-hole to accommodate a respective screw. Preferably, the portion comprises an essentially symmetric shape.

[0060] In order to facilitate a displacement of a portion of the material of the cylinder liner gasket and / or plastic deformation and / or to facilitate an improved pressure distribution, the cylinder liner gasket may be formed of materials having a different Young's modulus. Accordingly, in particular for portions of the cylinder liner gasket configured to be adjacent to a respective screw in the assembled state, a material comprising a lower Young's modulus may be present. In particular, the use of different materials for different portions of the cylinder liner gasket may hence facilitate a displacement of material upon an application of a predefined initial screwing force upon assembly, such that the cylinder liner gasket may efficiently adapt to any present inhomogeneous surfaces and manufacturing tolerances and / or locally occurring stresses.

[0061] According to a further aspect, a method for assembling a cylinder liner to a strongback of a combustion engine is provided.

[0062] The method comprises the steps of placing a cylinder liner gasket between a portion of a bottom surface of a flange portion of the cylinder liner and a top surface of the strongback; in the assembled state of the cylinder liner, mounting a cylinder head to the strongback so as to apply a screwing force to the cylinder liner gasket with a first predefined screwing force, thereby displacing at least a portion of the cylinder liner gasket; and mounting the cylinder head to the strongback by applying a second nominal screwing force being smaller than the first predefined screwing force.

[0063] By means of the application of the predefined initial screwing force, a displacement or biasing of one or more portions of the cylinder liner gasket occurs, which enables that the cylinder liner gasket may efficiently adapt to any present inhomogeneous surfaces and manufacturing tolerances and / or locally occurring stresses. As a result, a more homogeneous pressure distribution may be provided upon the application of the second nominal screwing force.

[0064] Since the second nominal screwing force is not intended to provide a displacement or biasing of the one or more portions, but may be applied to ensure a proper sealing between the cylinder liner and the strongback, the second nominal screwing force may typically be lower than the first predefined screwing force. For example, the second nominal screwing force may correspond to between 30 percent and 80 percent of the first screwing force.

[0065] Preferably, the screwing force is larger than zero between the application of the first screwing force and the application of the second screwing force. Thereby, after the partial displacement of the cylinder liner gasket, e.g. to conform to manufacturing tolerances and / or to distribute locally occurring stresses, a movement of the cylinder liner gasket relative to the flange portion of the cylinder liner and the top surface of the strongback may be avoided. Accordingly, an inadvertent mismatch of the one or more portions modified by the first screwing force to the surface of the flange portion and the top portion of the strongback may be effectively avoided.

[0066] Preferably, the cylinder liner gasket is a cylinder liner gasket according to the invention as described in the above.

[0067] Furthermore, the method may optionally comprise the step, wherein prior to the application of the first screwing force a cylinder head gasket, preferably made of metal, is placed between a top surface of a portion of the flange portion of the cylinder liner and a bottom surface of the cylinder head, wherein the cylinder head gasket comprises a varying thickness in the circumferential and / or radial direction.

[0068] Similar to the cylinder liner gasket described above, this may result in local differences in thickness and / or material density to advantageously counteract any inhomogeneous pressure distributions between the cylinder head and the cylinder liner. Accordingly, an even more homogeneous pressure distribution may be provided, resulting in an improved sealing towards the combustion space within the cylinder while avoiding or at least reducing the occurrence of any inadvertent deformations of the cylinder liner, in particular its flange portion, upon application of a required screwing force.Industrial Applicability

[0069] With reference to the Figures, a cylinder liner gasket for a cylinder liner of a combustion engine as well as a corresponding cylinder head assembly and assembly method using such cylinder liner gasket are suggested. The suggested cylinder liner gasket as mentioned above is applicable in a variety of engines, such as gas engines, wherein undesirable pressure distributions may occur at the region of the screwing engagement, potentially resulting in increased wear and / or leakage. The geometry and mechanical aspects of the cylinder liner gasket accommodate for these inhomogeneous pressure distributions, providing a more constant connection along the circumference of the cylinder liner gasket, thereby improving both sealing and wear characteristics. The disclosed cylinder liner gasket may be mounted between existing cylinder liners and strongbacks as a replacement or retrofit part, which may be exchanged e.g. upon or prior to overhaul or prior to use, or may be introduced at the factory site for the initial assembly of cylinder liners and strongbacks in a cylinder head assembly.

Examples

Embodiment Construction

[0012]In the following, the invention will be explained in more detail with reference to the accompanying figures. In the Figures, like elements are denoted by identical reference numerals and repeated description thereof may be omitted in order to avoid redundancies.

[0013]In Figure 1 a schematic cylinder head assembly 10 is shown in a longitudinal section. The cylinder head assembly 10 may e.g. be mounted in an engine block of a combustion engine to form a respective cylinder thereof. Accordingly, the cylinder head assembly 10 comprises a cylinder head 12, which is depicted as a rectangular structure merely for improved intelligibility and overview of the relative arrangement of the components of the cylinder head assembly 10. The cylinder head 12 is mounted on top of a cylinder liner 14, which forms an inner liner within a bore of a strongback 16. Accordingly, the bore of the strongback 16 preferably accommodates or surrounds the cylinder liner 14 while at the same time ensuring t...

Technical Field

[0001] The present invention pertains to a cylinder liner gasket for use in a combustion engine with a strongback as well as a corresponding cylinder head assembly and method for assembling the cylinder liner with a gasket. In particular, the cylinder liner gasket may effectively provide an improved sealing without introducing excessive wear of the cylinder liner and an adjacent strongback.Technological Background

[0002] One of the functions of the strongback in a cylinder head assembly is to conform to any deformation of the cylinder liner so as to avoid a relative movement between both parts. In this manner, the occurrence of wear at the connecting interface between the strongback and the cylinder liner may be considerably reduced or avoided to the largest possible extent. In particular, for engines without such strongback, i.e. with a direct contact of the cylinder liner to the engine block, it has been found considerably challenging to address this issue based on the typically very stiff engine block, which hence cannot conform to any deformation of the cylinder liner. Thereby, relative movements and corresponding wear may occur, ultimately resulting in a potential leaking of coolant or cooling water out of the engine.

[0003] However, on the other side, the strongback should also be stiff enough to minimize the occurrence of deformations of the cylinder liner, which may have an adverse impact on the combustion. For example, fourth order deformations of the cylinder liner may have the effect that the piston rings within the cylinder liner no longer function as intended, if they exceed a predetermined determined limit.

[0004] Attempts to address these issues and to e.g. increase the stiffness and improve the distribution of the stiffness of the strongback, e.g. to avoid such deformations of the cylinder liner, include the use of different materials. One such example includes the change from gray cast iron to spheroidal graphite iron. However, it has been found that such material change may simultaneously have an adverse effect on the tribology properties of the two parts, i.e. the cylinder liner and the strongback, such that the wear between these parts may increase based on a sliding movement, even if the extent of movement is not increased compared with previously used materials.

[0005] Accordingly, a need exists to reduce the occurrence of wear of the cylinder liner and / or the strongback while enabling a sufficient sealing to avoid leakage of coolant or combustible fluids.Summary of the Invention

[0006] Starting from the prior art, it is an objective to provide a new and inventive connection between the cylinder liner and a strongback of a combustion engine. In particular, it may be an objective to provide a means to reduce the occurrence of leakage while providing a sufficient conformability with reduced wear between the strongback and the cylinder liner.

[0007] This objective is solved by means of a cylinder head assembly, a cylinder liner gasket, and a method according to the features of the independent claims. Preferred embodiments are set forth in the present specification, the Figures as well as the dependent claims.

[0008] Accordingly, a cylinder head assembly for a combustion engine is suggested, comprising a cylinder head, a cylinder liner, and a strongback configured for attachment to the cylinder head and for accommodating the cylinder liner in the assembled state. An upper flange portion of the cylinder liner is arranged between the cylinder head and a portion of a top surface of the strongback facing the cylinder head in the assembled state and a cylinder liner gasket is arranged at least between a portion of the bottom surface of the flange portion of the cylinder liner and the top surface of the strongback.

[0009] Furthermore, a cylinder liner gasket is suggested that is configured for arrangement between a portion of a bottom surface of a flange portion of a cylinder liner and a top surface of a strongback of a combustion engine, wherein the cylinder liner gasket comprises a varying thickness and / or material density in the circumferential and / or radial direction.

[0010] According to a further aspect, a method for assembling a cylinder liner to a strongback of a combustion engine is suggested, comprising the steps of: placing a cylinder liner gasket between a portion of a bottom surface of a flange portion of the cylinder liner and a top surface of the strongback; in the assembled state of the cylinder liner, mounting a cylinder head to the strongback so as to apply a screwing force to the cylinder liner gasket with a first predefined screwing force, thereby displacing at least a portion of the cylinder liner gasket; and mounting the cylinder head to the strongback by applying a second nominal screwing force being smaller than the first predefined screwing force.Brief Description of the Drawings

[0011] The present disclosure will be more readily appreciated by reference to the following detailed description when being considered in connection with the accompanying drawings in which: Fig. 1 shows a schematic longitudinal section of a cylinder head assembly according to a preferred embodiment of the invention; Fig. 2 shows a cylinder liner gasket according to the invention according to an embodiment; and Fig. 3 shows a cylinder liner gasket according to the invention according to another embodiment. Detailed Description of Preferred Embodiments

[0012] In the following, the invention will be explained in more detail with reference to the accompanying figures. In the Figures, like elements are denoted by identical reference numerals and repeated description thereof may be omitted in order to avoid redundancies.

[0013] In Figure 1 a schematic cylinder head assembly 10 is shown in a longitudinal section. The cylinder head assembly 10 may e.g. be mounted in an engine block of a combustion engine to form a respective cylinder thereof. Accordingly, the cylinder head assembly 10 comprises a cylinder head 12, which is depicted as a rectangular structure merely for improved intelligibility and overview of the relative arrangement of the components of the cylinder head assembly 10. The cylinder head 12 is mounted on top of a cylinder liner 14, which forms an inner liner within a bore of a strongback 16. Accordingly, the bore of the strongback 16 preferably accommodates or surrounds the cylinder liner 14 while at the same time ensuring that at least around a portion of the cylinder liner 14 a cavity is defined, which may be used for the circulation of a coolant.

[0014] A top portion of the cylinder liner 14 extends radially outward forming a flange portion 18, which is arranged between the bottom surface of the cylinder head 12 and the top surface of the strongback 16. In this manner, the flange portion 18 of the cylinder liner 14 is compressed between the cylinder head 12 and the strongback 16. In order to provide an improved sealing between the flange portion 18 and the strongback 16, a cylinder liner gasket 20 is arranged between the bottom surface of the flange portion 18 and the top surface of the strongback 16.

[0015] According to the present example, the cylinder liner gasket 20 comprises a portion having a varying thickness 22, as indicated by the corresponding height in the longitudinal section. The portion with the varying thickness 22 mag e.g. comprise an increased thickness in the radially inward direction of the cylinder liner gasket 20. It will be understood that such varying thickness is not limited to the step-wise variation in thickness, as depicted in Figure 1, but a more gradual variation may be present instead.

[0016] The varying thickness may be adapted to the presence of one or more local stresses, which may occur upon assembly, wherein screws 24 provide an engagement between the cylinder head 12 and the strongback 16. The screws 24 are depicted to be received within the strongback 16. In particular, not shown in further detail in Figure 1, the screws 24 may extend through the strongback 16 towards a crank case (not shown) for a screwing engagement with respective threads within the crank case. The screwing engagement may typically result in larger screwing or compressive forces around the respective screws 24 compared with portions of the cylinder liner 14 and / or strongback 16 not being directly adjacent to the screws 24. As a result, an uneven pressure distribution may be present, potentially causing a leakage from the cavity between the cylinder liner 14 and the strongback 16 and / or an increase in wear in case of relative movement.

[0017] The portion with the varying thickness 22, e.g. having at least partially a different thickness than an adjacent portion of the cylinder liner gasket 20, effectively counteracts such uneven pressure distribution by ensuring that a more even connection between the surfaces adjacent to the cylinder liner gasket 20 are provided. This is because e.g. an increased thickness for those portions of the cylinder liner 14 otherwise not providing a sufficient sealing causes an increase in the locally applied screwing force while a reduced thickness around the screws 24 enables that focal stresses may be levelled out more evenly.

[0018] In the present, non-limiting embodiment, a cylinder head gasket 26 is furthermore arranged between a bottom surface of the cylinder head 12 and a top surface of the flange portion 18 of the cylinder liner 14. Such cylinder head gasket 26 may also comprise a portion 28 with a varying thickness and / or material density and ensures that upon assembly and the application of a nominal screwing force a sealing between the cylinder head 12 and the cylinder liner 14 may be improved. Accordingly, the risk of combustible fluids inadvertently leaking via the interface between the cylinder head 12 and the flange portion 18 of the cylinder liner 14 may be considerably reduced. Furthermore, the risk of inadvertent deformations of the flange portion 18 of the cylinder liner 14 upon application of the nominal screwing force may be reduced.

[0019] For both the cylinder liner gasket 20 and the cylinder head gasket 26 the portion 22, 28 having a varying thickness and / or material density may be at least partially present upon initial assembly. Preferably, the portion 22, 28 is at least partially formed based on the application of an initial predefined screwing force being larger than a subsequently applied nominal screwing force. The application of such initial predefined screwing force may hence result in a biasing or displacement of at least a portion of the cylinder liner gasket 20 and cylinder head gasket 26. Thereby, not only a more even pressure distribution may be achieved. The cylinder liner gasket 20 and the cylinder head gasket 26 also provide a level of adaptation to manufacturing tolerances and local height differences of the interfacing surfaces of the cylinder head 12, the cylinder liner 14 or flange portion 18 thereof, and the strongback 16.

[0020] In Figure 2 an example of a cylinder liner gasket 20 is shown for a strongback 16 configured for attachment with a cylinder head 12 in a configuration with four screws. As shown, the cylinder liner gasket 20 is essentially ring-shaped and provides a structure surrounding a bore 30 of the strongback 16. Furthermore, the cylinder liner gasket 20 comprises a total of four portions 22 having a varying thickness and / or material density, which essentially correspond to a respective portion of the strongback 16 configured to receive a screw 24 for engagement with the cylinder head 12. Accordingly, these portions 22 may each extend about 30 degrees in the circumferential direction and are equally spaced apart from each other in conformity with the arrangement of the screws 24.

[0021] In the example according to Figure 2 the cylinder liner gasket 20 is configured to surround the respective screws 24 within respective recesses 32. Thereby, any inhomogeneous local stresses at the level of the screws 24 and directly adjacent thereto may be distributed more evenly.

[0022] An alternative example of a cylinder liner gasket 20 is depicted in Figure 3, wherein the cylinder liner gasket 20 is also arranged directly adjacent to bores or through-holes 34 of the strongback 16, but comprises the corresponding portions with a varying thickness and / or material density only at the radially inward side. In other words, the portions 22 may optionally directly abut the respective screws 25 in the assembled state, but do not surround or fully enclose the screws 24. Alternatively, the cylinder liner gasket 20 may also be formed and arranged so as to define a predefined spacing or small gap to the respective screws, which may depend on the effect of the application of the screwing force upon assembly, in particular an initial predefined screwing force applied to displace or bias a portion of the cylinder liner gasket 20.

[0023] It will be understood that the portions 22 may also be formed with recesses 32 having a C-shape or U-shape, such that the portions may at least partially surround the respective screws 24. Such a configuration may also be advantageous to facilitate and monitor the arrangement of the cylinder liner gasket 20 and its portions 22 relative to the respective bores or through-holes 34 of the strongback 16.

[0024] It will be obvious for a person skilled in the art that these embodiments and items only depict examples of a plurality of possibilities. Hence, the embodiments shown here should not be understood to form a limitation of these features and configurations. Any possible combination and configuration of the described features can be chosen according to the scope of the invention.

[0025] This is in particular the case with respect to the following optional features which may be combined with some or all embodiments, items and / or features mentioned before in any technically feasible combination.

[0026] A cylinder head assembly for a combustion engine is provided.

[0027] The cylinder head assembly comprises a cylinder head, a cylinder liner, and a strongback configured for attachment to the cylinder head and for accommodating the cylinder liner in the assembled state. An upper flange portion of the cylinder liner is arranged between the cylinder head and a portion of a top surface of the strongback facing the cylinder head in the assembled state and a cylinder liner gasket is arranged at least between a portion of the bottom surface of the flange portion of the cylinder liner and the top surface of the strongback.

[0028] According to the present invention it has been found that the placement of a cylinder liner gasket between the adjacent surfaces of the cylinder liner and the strongback enables that an improved pressure distribution of the connecting interface may be provided.

[0029] To further facilitate the improved pressure distribution of the connecting interface, the cylinder liner gasket preferably comprises a varying thickness and / or material density in the circumferential and / or radial direction. Based on the varying thickness and / or material density of the cylinder liner gasket, a pressure may be distributed in a more homogenous manner. This is because the varying thickness and / or material density of the cylinder liner gasket may compensate for any local pressure differences occurring during the screwing engagement of the cylinder head.

[0030] In other words, for positions on the cylinder liner surface and strongback surface that would typically be associated with a reduced local pressure the cylinder liner gasket may be adapted to locally provide e.g. a corresponding increased thickness, such that, in the assembled state under screwing engagement, e.g. provided by screws inserted in the cylinder head and extending through the strongback for a screwing engagement with respective threads in a crank case, a larger pressure may be present at such positions, thereby providing a more even pressure distribution. By the same token, the cylinder liner gasket may e.g. comprise a reduced thickness at portions corresponding to a typically increased local pressure to accordingly reduce the pressure.

[0031] By enabling the improved pressure distribution, the risk of occurring leakages may be effectively reduced, since a sufficient pressure may be ensured along the entire circumference of the cylinder liner gasket and hence between the cylinder liner and the strongback. For example, coolant or cooling water present in a cavity between the cylinder liner and the strongback is blocked from leaking out of said cavity due to advantageous configuration of the cylinder liner gasket.

[0032] Furthermore, the level of deformation of the cylinder liner that may occur when e.g. the cylinder head engages the strongback may be reduced based on the cylinder liner gasket, since focal pressures and corresponding biases, in particular of the flange portion of the cylinder liner, may be avoided or at least be more evenly distributed. Thereby, an improved interface may be maintained between the cylinder liner and the cylinder head, such that the risk of inadvertent leakage of a combustion fluid may be considerably reduced.

[0033] At the same time, any deformations occurring to cylinder liner may still be accommodated by the strongback, since based on the implementation of the cylinder liner gasket no adaptations are required to the structure and material of the strongback.

[0034] In the assembled state the cylinder liner is preferably accommodated or housed within a bore of the strongback, such that the strongback may surround the cylinder liner. The cylinder liner is preferably at least partially accommodated by means of an interference fit. The flange portion may accordingly extend over a top surface of the strongback and may be brought in a sandwiched construction between said surface of the strongback and an adjacent surface of the cylinder head at an opposing side of the flange portion.

[0035] The cylinder liner gasket is preferably formed as a ring-shaped element, such that a continuous structure is provided in the circumferential direction. Preferably, the cylinder liner gasket is exclusively arranged between a portion of the bottom surface of the flange portion of the cylinder liner and the top surface of the strongback, such that it is preferably designed to provide an adaptation only for any otherwise occurring pressure differences, yet does not inadvertently interfere with further parts or components.

[0036] Preferably, the strongback is configured receive a plurality of screws, wherein the cylinder liner gasket surrounds at least a portion of each of the screws or is arranged adjacent to a portion of each of the screws in the assembled state.

[0037] For example, the flange portion may be clamped between the strongback and the cylinder head, wherein a plurality of bores may be present in the flange portion to receive a corresponding number of screws. The screws may be received by corresponding through-holes in the strongback and may extend through the screwback to provide a screwing engagement with corresponding threads within a crank case.. The configuration of the cylinder liner gasket may accordingly comprise a corresponding number of recesses, which are C-shaped, U-shaped or be essentially formed as a through-hole to accordingly at least partially accommodate a corresponding screw.

[0038] Alternatively, the cylinder liner gasket may be formed and positioned to provide an abutment to each of the respective screws while essentially extending radially inward, forming a radial inner sealing without extending at least partially around each of the screws. The configuration may be based on the required pressure distribution.

[0039] In this regard, a portion of the cylinder liner gasket adjacent the screws preferably comprises a reduced thickness and / or an increased material density. For example, a reduced thickness around a least a portion of each screw may ensure that, upon screwing engagement and the application of a screwing and / or clamping force, a typically occurring locally increased pressure around the screw may be reduced while at the same time enabling that a force and corresponding pressure may be increased for portions of the cylinder liner and strongback that are not directly adjacent to the screws. Accordingly, the modification of the cylinder liner gasket around each of the screws provides an adaptation that may result in an improved pressure distribution and hence a more even sealing between the cylinder liner and the strongback.

[0040] By the same token, an increased material density may result from the application of a predefined screwing force causing a local material displacement and or plastic deformation within the portion of the cylinder liner gasket. The surface of the portion of the cylinder liner gasket may define a plane, e.g. with an inclination or declination, wherein the local material density may be adapted to the local focal pressure upon application of the screwing and / or clamping force. Portions with a lower material density may furthermore optionally define a less stiff portion with improved elasticity or resilience, which may further facilitate a more even pressure distribution.

[0041] Depending on the configuration of the cylinder head, the cylinder liner, and the strongback, multiple portions of the cylinder liner gasket may comprise a reduced thickness and / or an increased material density. In particular, each of said portions of the cylinder liner gasket may extend between 20 degrees and 50 degrees of the circumference of the cylinder liner gasket. Alternatively or in addition, said portions of the cylinder liner gasket may be equally spaced-apart from each other along the circumference of the cylinder liner gasket.

[0042] For example, the circumferential extension of each portion may correspond to a corresponding portion of the cylinder liner and / or strongback experiencing a larger pressure, such that the reduced thickness and / or increased material density may provide a reduced pressure and corresponding more even distribution along the circumferential direction. The thickness and / or material density may furthermore vary in the radial direction, such that e.g. stress focal points may be accordingly reduced in the radial direction and / or may be biased towards a radial inner potion for improved sealing. Preferably, the portions are not only equally spaced apart from each other, but also equally distributed relative to adjacent and / or interfacing the cylinder liner and strongback surfaces.

[0043] Preferably, each of said portions corresponds to a portion of the top surface of the strongback configured to receive a screw in the assembled state. For example, the cylinder head assembly may be mounted using four screws. Accordingly, the circumferential extension of each portion may comprise e.g. between 20 degrees and 40 degrees while the circumferential extension of the portions between the portions having a reduced thickness and / or increased material density may comprise e.g. between 50 degrees and 70 degrees. For assemblies requiring six screws or eight screws the extension of the former portions may be accordingly reduced.

[0044] As described above, the portions may advantageously comprise a corresponding recess, e.g. being C-shaped, U-shaped, or shaped as a through-hole to accommodate a respective screw. Preferably, the portion comprises an essentially symmetric shape.

[0045] Preferably, the cylinder liner gasket is formed of a metal or metal alloy. Such material may have the advantage that an improved adaptability and conformability to local pressures and / or sufficient plastic deformation upon the respective pressures received may be provided. A metal-based cylinder liner gasket may also provide improved robustness and / or resilience. The material may be chosen according to the required conformability and / or the operating conditions and configuration of the combustion engine.

[0046] In order to provide an improved fitting of the cylinder liner gasket that is adapted to the respective cylinder head assembly and which takes into account any manufacturing tolerances, the varying thickness and / or the varying material density of the cylinder liner gasket is preferably formed by the application of an initial screwing force for the screwing engagement that is larger than a subsequent application of a nominal screwing force in the assembled state.

[0047] Accordingly, a displacement of the material may be provided by the predefined initial screwing force, which may result e.g. in a reduced thickness around those areas being subjected to the largest screwing force or stress. In other words, the cylinder liner gasket may be formed by a material flow or displacement, wherein more material with a corresponding larger thickness may accumulate at those areas otherwise being subjected to a lower screwing force. Thereby, upon application of the nominal screwing force, a more even pressure distribution with a corresponding improved sealing may be provided.

[0048] The material of the cylinder liner gasket may furthermore be adapted to enable such material displacement and / or may be chosen to further optimize the tribology in view of the adjacent cylinder liner and strongback, e.g. to anticipate or alleviate wear based on any relative movement or sliding.

[0049] In this regard, the cylinder liner gasket may also be formed of materials having a different Young's modulus. Accordingly, different stiffness and resilience properties may be provided, which may not only be advantageous upon the application of an initial predefined screwing force, but independently also to distribute stresses and pressures more evenly in the assembled state of the cylinder liner gasket and the cylinder head assembly as a whole.

[0050] To further improve the pressure distribution, also between the cylinder liner and the cylinder head, the cylinder head assembly may further comprise a cylinder head gasket being arranged at least between a top surface of a portion of the flange portion of the cylinder liner and a bottom surface of the cylinder head, wherein the cylinder head gasket comprises a varying thickness in the circumferential and / or radial direction.

[0051] Similar to the cylinder liner gasket described above, such local differences in thickness and / or material density advantageously effectively counteract any inhomogeneous pressure distributions between the cylinder head and the cylinder liner. Accordingly, a more even pressure distribution may be provided, resulting in an improved sealing while avoiding or at least reducing the occurrence of any inadvertent deformations of the cylinder liner, in particular its flange portion, upon application of a required screwing force. By means of the improved sealing the risk of leakage of combustible fluids via the interface between the cylinder head and the cylinder liner may be considerably reduced.

[0052] The implementation of both the cylinder liner gasket and the cylinder head gasket has furthermore been found to be synergistic in providing an improved pressure distribution in the two connections between the cylinder liner and the strongback and the cylinder liner and the cylinder head, potentially resulting in an even lower deformation of the cylinder liner and further wear reduction.

[0053] According to a further aspect, a cylinder liner gasket is provided, preferably a metal cylinder liner gasket.

[0054] The cylinder liner gasket is configured for arrangement between a portion of a bottom surface of a flange portion of a cylinder liner and a top surface of a strongback of a combustion engine, wherein the cylinder liner gasket comprises a varying thickness and / or material density in the circumferential and / or radial direction.

[0055] As described above, the cylinder liner gasket may advantageously improve a pressure distribution between the cylinder liner and the strongback. In this regard, the varying thickness and / or material density may compensate for any focal stresses caused by locally increased screwing forces, in particular around or at screws in case of a screwing engagement of a cylinder head and a strongback. The varying thickness, for example, may be present prior to the application of an initial predefined screwing force, wherein the screwing force may bias a portion of the material of the cylinder liner gasket, resulting e.g. in a modified thickness distribution of the cylinder liner gasket. In such manner, a connection or contact between the cylinder liner and the strongback for adjacent portions of the cylinder liner gasket may be improved, thereby providing a more homogeneous pressure distribution.

[0056] Alternatively, the cylinder liner gasket may also be formed as an essentially plane surface having an essentially homogeneous thickness prior to the application of an initial screwing force, wherein a thickness around or at the screws may be reduced upon the application of said screwing force, for example by plastic deformation, hence resulting in the varying thickness and / or material density.

[0057] Accordingly, portions of the cylinder liner gasket are preferably configured to be displaced in a predefined direction upon application of a predefined compression force. This predefined direction may particularly correspond to a direction away from a corresponding edge or recess configured to be adjacent to a screw upon assembly of a cylinder head assembly, such that the local stress around each of such screws may be effectively reduced and an improved pressure may be established at those portions of the cylinder liner gasket not being adjacent to the respective screw.

[0058] Each of said portions may extend between 20 degrees and 50 degrees of the circumference of the cylinder liner gasket and / or said portions may be equally spaced-apart from each other along the circumference of the cylinder liner gasket.

[0059] As described above, the circumferential extension of each portion may correspond to a corresponding portion of the cylinder liner and / or strongback experiencing a larger pressure, such that the reduced thickness and / or increased material density may provide a reduced pressure and corresponding more even distribution along the circumferential direction. Preferably, the portions are not only equally spaced apart from each other, but also equally distributed relative to adjacent and / or interfacing the cylinder liner and strongback surfaces. For example, each of said portions may correspond to a portion of the top surface of the strongback configured to receive a screw in the assembled state, such that for a cylinder head assembly to be mounted using four screws the circumferential extension of each portion may comprise e.g. between 20 degrees and 40 degrees while the circumferential extension of the portions between the portions having a reduced thickness and / or increased material density may comprise e.g. between 50 degrees and 70 degrees. Furthermore, each of said portions may comprise a corresponding recess, e.g. being C-shaped, U-shaped, or shaped as a through-hole to accommodate a respective screw. Preferably, the portion comprises an essentially symmetric shape.

[0060] In order to facilitate a displacement of a portion of the material of the cylinder liner gasket and / or plastic deformation and / or to facilitate an improved pressure distribution, the cylinder liner gasket may be formed of materials having a different Young's modulus. Accordingly, in particular for portions of the cylinder liner gasket configured to be adjacent to a respective screw in the assembled state, a material comprising a lower Young's modulus may be present. In particular, the use of different materials for different portions of the cylinder liner gasket may hence facilitate a displacement of material upon an application of a predefined initial screwing force upon assembly, such that the cylinder liner gasket may efficiently adapt to any present inhomogeneous surfaces and manufacturing tolerances and / or locally occurring stresses.

[0061] According to a further aspect, a method for assembling a cylinder liner to a strongback of a combustion engine is provided.

[0062] The method comprises the steps of placing a cylinder liner gasket between a portion of a bottom surface of a flange portion of the cylinder liner and a top surface of the strongback; in the assembled state of the cylinder liner, mounting a cylinder head to the strongback so as to apply a screwing force to the cylinder liner gasket with a first predefined screwing force, thereby displacing at least a portion of the cylinder liner gasket; and mounting the cylinder head to the strongback by applying a second nominal screwing force being smaller than the first predefined screwing force.

[0063] By means of the application of the predefined initial screwing force, a displacement or biasing of one or more portions of the cylinder liner gasket occurs, which enables that the cylinder liner gasket may efficiently adapt to any present inhomogeneous surfaces and manufacturing tolerances and / or locally occurring stresses. As a result, a more homogeneous pressure distribution may be provided upon the application of the second nominal screwing force.

[0064] Since the second nominal screwing force is not intended to provide a displacement or biasing of the one or more portions, but may be applied to ensure a proper sealing between the cylinder liner and the strongback, the second nominal screwing force may typically be lower than the first predefined screwing force. For example, the second nominal screwing force may correspond to between 30 percent and 80 percent of the first screwing force.

[0065] Preferably, the screwing force is larger than zero between the application of the first screwing force and the application of the second screwing force. Thereby, after the partial displacement of the cylinder liner gasket, e.g. to conform to manufacturing tolerances and / or to distribute locally occurring stresses, a movement of the cylinder liner gasket relative to the flange portion of the cylinder liner and the top surface of the strongback may be avoided. Accordingly, an inadvertent mismatch of the one or more portions modified by the first screwing force to the surface of the flange portion and the top portion of the strongback may be effectively avoided.

[0066] Preferably, the cylinder liner gasket is a cylinder liner gasket according to the invention as described in the above.

[0067] Furthermore, the method may optionally comprise the step, wherein prior to the application of the first screwing force a cylinder head gasket, preferably made of metal, is placed between a top surface of a portion of the flange portion of the cylinder liner and a bottom surface of the cylinder head, wherein the cylinder head gasket comprises a varying thickness in the circumferential and / or radial direction.

[0068] Similar to the cylinder liner gasket described above, this may result in local differences in thickness and / or material density to advantageously counteract any inhomogeneous pressure distributions between the cylinder head and the cylinder liner. Accordingly, an even more homogeneous pressure distribution may be provided, resulting in an improved sealing towards the combustion space within the cylinder while avoiding or at least reducing the occurrence of any inadvertent deformations of the cylinder liner, in particular its flange portion, upon application of a required screwing force.Industrial Applicability

[0069] With reference to the Figures, a cylinder liner gasket for a cylinder liner of a combustion engine as well as a corresponding cylinder head assembly and assembly method using such cylinder liner gasket are suggested. The suggested cylinder liner gasket as mentioned above is applicable in a variety of engines, such as gas engines, wherein undesirable pressure distributions may occur at the region of the screwing engagement, potentially resulting in increased wear and / or leakage. The geometry and mechanical aspects of the cylinder liner gasket accommodate for these inhomogeneous pressure distributions, providing a more constant connection along the circumference of the cylinder liner gasket, thereby improving both sealing and wear characteristics. The disclosed cylinder liner gasket may be mounted between existing cylinder liners and strongbacks as a replacement or retrofit part, which may be exchanged e.g. upon or prior to overhaul or prior to use, or may be introduced at the factory site for the initial assembly of cylinder liners and strongbacks in a cylinder head assembly.

Examples

Embodiment Construction

[0012]In the following, the invention will be explained in more detail with reference to the accompanying figures. In the Figures, like elements are denoted by identical reference numerals and repeated description thereof may be omitted in order to avoid redundancies.

[0013]In Figure 1 a schematic cylinder head assembly 10 is shown in a longitudinal section. The cylinder head assembly 10 may e.g. be mounted in an engine block of a combustion engine to form a respective cylinder thereof. Accordingly, the cylinder head assembly 10 comprises a cylinder head 12, which is depicted as a rectangular structure merely for improved intelligibility and overview of the relative arrangement of the components of the cylinder head assembly 10. The cylinder head 12 is mounted on top of a cylinder liner 14, which forms an inner liner within a bore of a strongback 16. Accordingly, the bore of the strongback 16 preferably accommodates or surrounds the cylinder liner 14 while at the same time ensuring t...

Claims

1. A cylinder head assembly (10) for a combustion engine, comprising: a cylinder head (12), a cylinder liner (14), and a strongback (16) configured for attachment to the cylinder head (12) and for accommodating the cylinder liner (14) in the assembled state, wherein an upper flange portion (18) of the cylinder liner (14) is arranged between the cylinder head (12) and a portion of a top surface of the strongback (16) facing the cylinder head (12) in the assembled state and wherein a cylinder liner gasket (20) is arranged at least between a portion of the bottom surface of the flange portion (18) of the cylinder liner (14) and the top surface of the strongback (16).

2. The cylinder head assembly (10) according to claim 1, wherein the cylinder liner gasket (20) has a varying thickness and / or material density in the circumferential and / or radial direction.

3. The cylinder head assembly (10) according to claim 1 or 2, wherein the strongback (16) is configured to receive a plurality of screws (24) and wherein the cylinder liner gasket (20) surrounds at least a portion of each of the screws (24) or is arranged adjacent to a portion of each of the screws (24) in the assembled state.

4. The cylinder head assembly (10) according to claim 3, wherein a portion (22) of the cylinder liner gasket (20) adjacent the screws (24) comprises a reduced thickness and / or an increased material density.

5. The cylinder head assembly (10) according to any of the preceding claims, wherein multiple portions (22) of the cylinder liner gasket (20) comprise a reduced thickness and / or an increased material density, wherein each of said portions (22) of the cylinder liner gasket (20) extends between 20 degrees and 50 degrees of the circumference of the cylinder liner gasket (20) and / or wherein said portions (22) of the cylinder liner gasket (20) are equally spaced-apart from each other along the circumference of the cylinder liner gasket (20).

6. The cylinder head assembly (10) according to claim 5, wherein each of said portions (22) corresponds to a portion of the top surface of the strongback (24) configured to receive a screw (24) in the assembled state.

7. The cylinder head assembly (10) according to any of the preceding claims, wherein the varying thickness and / or the varying material density of the cylinder liner gasket (20) is formed by the application of an initial screwing force for the screwing engagement that is larger than a subsequent application of a nominal screwing force in the assembled state.

8. The cylinder head assembly (10) according to any of the preceding claims, wherein the cylinder liner gasket (20) is formed of materials having a different Young's modulus.

9. The cylinder head assembly (10) according to any of the preceding claims, further comprising a cylinder head gasket (26) being arranged at least between a top surface of a portion of the flange portion (18) of the cylinder liner (14) and a bottom surface of the cylinder head (12), the cylinder head gasket (26) having a varying thickness in the circumferential and / or radial direction.

10. The cylinder head assembly (10) according to any of the preceding claims, wherein the cylinder liner gasket (10) is formed of a metal or metal alloy.

11. A cylinder liner gasket (20) configured for arrangement between a portion of a bottom surface of a flange portion (18) of a cylinder liner (14) and a top surface of a strongback (16) of a combustion engine, wherein the cylinder liner gasket (20) comprises a varying thickness and / or material density in the circumferential and / or radial direction.

12. The cylinder liner gasket (20) according to claim 11, wherein portions (22) of the cylinder liner gasket (20) are configured to be displaced in a predefined direction upon application of a predefined compression force.

13. The cylinder liner gasket (20) according to claim 12, wherein each of said portions (22) extends between 20 degrees and 50 degrees of the circumference of the cylinder liner gasket (20) and / or wherein said portions (22) are equally spaced-apart from each other along the circumference of the cylinder liner gasket (20).

14. The cylinder liner gasket (20) according to any of claims 11 to 13, wherein the cylinder liner gasket (20) is formed of materials having a different Young's modulus.

15. A method for assembling a cylinder liner (14) to a strongback (16) of a combustion engine, comprising the steps of: - placing a cylinder liner gasket (20) between a portion of a bottom surface of a flange portion (18) of the cylinder liner (14) and a top surface of the strongback (16); - in the assembled state of the cylinder liner (14), mounting a cylinder head (12) to the strongback (16) so as to apply a screwing force to the cylinder liner gasket (20) with a first predefined screwing force, thereby displacing at least a portion (22) of the cylinder liner gasket (20); and - mounting the cylinder head (12) to the strongback (16) by applying a second nominal screwing force being smaller than the first predefined screwing force.

16. The method according to claim 15, wherein the screwing force is larger than zero between the application of the first screwing force and the application of the second screwing force.

17. The method according to claim 15 or 16, wherein the cylinder liner gasket (20) is a cylinder liner gasket (20) according to any of claims 11 to 14.

18. The method according to any of claims 15 to 17, wherein prior to the application of the first screwing force a cylinder head gasket (26) is placed between a top surface of a portion of the flange portion (18) of the cylinder liner (14) and a bottom surface of the cylinder head (12), wherein the cylinder head gasket (26) comprises a varying thickness in the circumferential and / or radial direction.

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