CRANKSHAFT SEAL UNIT FOR AN INTERNAL COMBUSTION ENGINE

Technical Field

The present invention refers to a crankshaft seal unit for an internal combustion engine and to an internal combustion engine which is equipped with such a crankshaft seal unit.

Technological Background

Reciprocating internal combustion engines are equipped with a crankshaft which is usually housed in a crankcase at a bottom of an engine block. The crankshaft is configured to convert reciprocating motion of pistons within cylinders of the engine into rotational movement which is to be transferred to a component to be driven via a crankshaft flange. For doing so, the crankshaft protrudes through an opening in a crankcase wall such that the crankshaft flange is located outside the crankcase, thereby constituting a structural interface which is accessible from outside the engine to be coupled to the component to be driven.

For preventing fluids present in the crankcase, such as lubricating oil, from being expelled through the opening in the crankcase wall, such engines are equipped with a crankshaft seal disposed between the crankshaft and the opening. According to a common configuration, the crankshaft seal is provided in the form of a labyrinth seal.

In general, labyrinth seals refer to non-contact shaft seals, the sealing effect of which is based on providing a tortuous path and thus inducing high flow resistances for a fluid when passing through the gap between the crankshaft and the opening in the wall. Typically, for achieving this effect, the labyrinth seal comprises a plurality of radially extending teeth or groves that press tightly inside a correspondingly designed structure. By this interlock between the components, a fluid has to pass through a long and tortuous path which significantly reduces its kinetic energy upon flowing therethrough, thereby preventing leakage of the fluid.

For labyrinth seals on rotating shafts, such as crankshafts, the path through the labyrinth sealing must have a relatively small clearance in order to ensure proper sealing effect. This requires precise manufacturing and thus may be costly. However, during operation of the engine, such seals are subjected to fatigue and thus, with progressing lifetime of the engine, the provided sealing effect may be decreased.

Summary of the Disclosure

Starting from the prior art, it is an objective to provide an improved crankshaft seal unit for an internal combustion engine, which in particular provides an improved sealing effect. Further, it is an objective to provide an internal combustion engine which is equipped with such a crankshaft seal unit.

These objectives are solved by means of the subject matter of the independent claims. Preferred embodiments are set forth in the present specification, the Figures as well as the dependent claims.

Accordingly, a crankshaft seal unit for an internal combustion engine is provided. The crankshaft seal unit comprises a seal which, in a mounted state in which the crankshaft seal unit is mounted to the engine, is configured to provide sealing between a crankshaft and a crankcase of the engine, and a fan element which is configured to be mounted to the crankshaft in the crankcase.

Furthermore, an internal combustion engine is provided which is equipped with such a crankshaft seal unit.

Since the proposed internal combustion engine comprises the above described crankshaft seal unit, technical features which are described in connection with the crankshaft seal unit in the present disclosure may also relate and be applied to the proposed internal combustion engine, and vice versa. Brief Description of the Drawings

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 schematically shows a partial view along a longitudinal section through a crankshaft sealing unit which is mounted to an internal combustion engine between a crankshaft and a cylinder crankcase of the engine;

Fig. 2 schematically shows a perspective view of a fan element used in the crankshaft sealing unit depicted in Figure 1; and

Fig. 3 schematically shows an enlarged section B of Figure 2.

Detailed Description of Preferred Embodiments

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.

Figure 1 depicts a longitudinal section through an internal combustion engine 10, also referred to as the “engine” in the following, provided in the form of a reciprocating engine. The engine 10 is intended and configured to be installed in a vessel or power plant and may be used as a main or auxiliary engine.

The engine 10 comprises a plurality of cylinders (not shown), e.g. twelve or sixteen or eighteen cylinders, which are received in an engine block and which are arranged according to an in-line configuration or any other known cylinder configuration. Each cylinder is provided with a combustion chamber delimited by a piston accommodated in the cylinder. The pistons are configured for reciprocating and axial movement within the cylinders and are coupled to a crankshaft 12 via piston connecting rods. During operation of the engine 10, fuel, such as diesel or natural gas, and air are supplied to and ignited in each cylinder so as to produce high-temperature and high-pressure gases which apply forces to and thus axially move the corresponding pistons, thereby rotating the crankshaft 12. In this way, chemical energy is transformed into mechanical energy.

For transferring the thus generated mechanical energy to a component to be driven, such as to a ship’s propeller (not shown), the crankshaft 12 comprises a crankshaft flange 14 which constitutes a structural interface configured to be coupled to the component to be driven by the engine 10.

The crankshaft 12 is housed in a crankcase 16, also referred to as cylinder crankcase. Specifically, in a mounted state of the engine in which it is installed, the crankcase 16 is located at a bottom of the engine 10 and mounted to or integrated into the engine block. The crankcase 16 forms an oil sump at its bottom which contains engine’s lubricating oil.

The crankshaft flange 14 is located outside the crankcase 16 so as to ensure good accessibility and to facilitate coupling to the component to be driven. For doing so, the crankshaft 12 protrudes through an opening 18 in a crankcase wall 20 such that the crankshaft flange 14 is located outside the crankcase 16. In this way, the crankshaft flange 14 is accessible from outside the engine 10 to be coupled to the component to be driven. Specifically, the opening 18 is provided in an end cover 24 of the crankcase 16 which is releasably mounted thereto.

The basic and general structure, and function of such an internal combustion engine 10 and its components are well known to a person skilled in the art and are thus not further specified. Rather, a crankshaft seal unit 26, also referred to as the "seal unit " in the present disclosure, is addressed in the following which is interlinked with the present disclosure.

For preventing unintentional discharge of the lubricating oil from an inside 22 of the crankcase 16 through the opening 18, i.e. through a gap between the crankshaft flange 14 and the opening 18, the seal unit 26 is provided. The seal unit 26 is configured to seal the inside 22 of the crankcase 16 from an outside of the engine 10 so as to prevent that an unintended exchange of fluids, such as the lubricating oil or gas present in the crankcase 16, occurring via the gap between the crankshaft 12 and the crankcase 16.

The seal unit 26 comprises a seal 28 which provides sealing between the crankshaft 12 and the crankcase 16, i.e. between the crankshaft flange 16 and the end cover 24 of the crankcase 16. In other words, in the mounted state as shown in Fig. 1 in which the seal unit 26 is mounted to the engine 10, the seal 28 provides sealing between the crankshaft 12 and the crankcase 16. Specifically, the seal 28 is provided in the form of a labyrinth seal which is disposed between and constituted by the inner surface or wall of the opening 18 and the outer surface of the crankshaft 12, in particular the crankshaft flange 14. As can be gathered from Fig. 1, the outer surface of the crankshaft 12, in particular the crankshaft flange 14, is provided with a plurality of teeth or grooves which extend radially and circumferentially around the crankshaft 12 and which are arranged next to one another along a longitudinal axis X of the crankshaft 12. The inner surface of the opening 18 at the end cover 24 is correspondingly designed to the plurality of teeth or grooves at the crankshaft 12 so as to interlock and thereby forming a tortuous path for fluids through the gap between the crankshaft 12, i.e. the crankshaft flange 14, and the opening 18 provided in the end cover 24 of the crankcase 16.

The end cover 24 is provided with an inner front face 30 which, when viewed from a direction pointing from the crankshaft flange 14 along the longitudinal axis X towards the inside 22 of the crankcase 16, is arranged after the seal 28. The front face 30 extends circumferentially around and in a radial direction in view of the longitudinal axis X of the crankshaft 12. Further, the front face 30 faces the inside 22 of the crankcase 16. Specifically, in the shown configuration, the front face 30 extends perpendicular to the longitudinal axis X. In other words, a surface normal of the front face 30 is parallel to the longitudinal axis X. In this way, the front face 30 constitutes a ring-shaped surface which lies within a plane extending perpendicular to the longitudinal axis X. For being provided with such a structural configuration, the end cover 24 comprises a circumferentially extending side wall 32 which radially delimits the opening 18, wherein at an inner end thereof the front face 30 is provided. Specifically, in a longitudinal section through the end cover 24 as depicted in Fig. 1, the side wall 32 is provided with an L-shaped profile.

According to an alternative configuration, the end cover 24 may be provided such that the surface normal of the front surface 30 may be inclined relative to the longitudinal axis X, in particular such that the front face 30 tapers along the longitudinal axis X when viewed from inside 22 of the crankcase 16 towards the crankshaft flange 14, or vice versa.

Further, the seal unit 26 is provided with a fan element 34 which is releasably mounted to the crankshaft 12. In the shown configuration, the fan element 34 is provided in the form of a fan wheel mounted around the crankshaft 12. Specifically, the fan element 34 is mounted around the crankcase 12 such that the fan element 34 is positioned in the crankcase 16, i.e. in the inside 22 of the crankcase 16. In other words, in the mounted state of the seal unit 26, the fan element 34 is located within the crankcase 16.

As can be gathered from Fig. 1, the fan element 34 is fixedly mounted to an inner front end of the crankshaft flange 14, i.e. which is oriented towards the inside 22 of the crankcase 16, by a plurality of fixing means, i.e. screws. That is, the fan element 34 is torque-transmittingly mounted to the crankshaft flange 14 such that the fan element 34 rotates together with the crankshaft 12 during operation of the engine 10.

Specifically, the inner front end of the crankshaft flange 14 is provided with a ring-shaped surface which is in tight contact with the fan element 34. In an area within the ring-shaped surface, the inner front end of the crankshaft flange 14 is connected and fixed to a drive shaft 36 of the crankshaft 12. Accordingly, the fan element 34 is provided in the area of a connection between the crankshaft flange 14 and the drive shaft 36 of the crankshaft 12. More specifically, the fan element 34 is provided around the connection between the crankshaft flange 14 and the drive shaft 36 of the crankshaft 12. By such a configuration, the proposed fan element 34 can be releasably mounted to the crankshaft 12. Further, in the mounted state, the longitudinal axis X of the crankshaft 12 and a longitudinal axis of the fan element 34 coincide.

The fan element 34 is arranged in front of the seal 28 such that it faces the inner side of the seal 28. In other words, the fan element 34 is arranged next to the inner side of the seal 28 along a longitudinal axis X of the crankshaft 12. Further, the fan element 34 is arranged in front of the front face 30 of the end cover 24 such that the front face 30 and the fan element 34, i.e. fan blades 38 thereof, face each other, i.e. are arranged opposing to one another.

The fan element 34 is designed such that upon rotating together with the crankshaft 12 around its longitudinal axis, the fan element 34, i.e. by means of its fan blades 38, generates a pressure gradient among the fan element 34. That is, on a first side of the fan element 34 which faces the seal 28, a pressure level prevails which is smaller compared to a pressure level prevailing on an opposed second side of the fan element 34, i.e. which faces away from the seal 28. Specifically, the fan element 34 is configured such that, upon being rotated around the longitudinal axis X, the fan element 34, i.e. by means of its fan blades 38, subjects the inner side of the seal 28 to a pressure drop. In other words, the fan element 34, upon rotation, generates a negative pressure, also referred to as under pressure or vacuum, which prevails at the first side of the fan element 34 and thus at an inner side of the seal 28, i.e. which faces the inside 22 of the crankcase 16. In the context of the present disclosure, the terms “negative pressure”, “under pressure” or “vacuum” refer to a pressure level which is lower compared to an average pressure level prevailing within the crankcase 16.

Due to the pressure gradient generated among the fan element 34 upon being rotated together with the crankshaft 12, a fluid stream is generated having a flow direction which is directed from the first side of the fan element 34 facing the seal 28 through the fan element 34 to its second side. In other words, the thus induced fluid stream flows from the inner side of the seal 28 through the fan element 34.

For inducing the described pressure gradient among the fan element 34 during operation of the engine 10, i.e. upon rotational actuation, the fan element 34 and its fan blades 38 are provided with a geometric configuration which is described in the following with reference to Fig. 2 which shows a perspective view of the fan element 34. It is apparent to the skilled person that the fan element 34 depicted in Fig. 2 refers to one exemplary embodiment to achieve the above described advantageous effects and that the present disclosure is not limited to this specific configuration.

In the shown configuration, the fan element 34 is provided as a disc shaped component, in particular a ring-shaped disc, which is made of a metal sheet, wherein the fan blades 38 may be produced by a cutting and a forming process. As can be gathered from Fig. 2, the fan element 34 can be subdivided into two adjacent circumferential band sections, i.e. an inner band section and an outer band section.

The inner band section, i.e. which is arranged radial inwardly, is provided with a plurality of mounting recesses 40 which are arranged according to a regular pattern. That is, four groups 42 of mounting recesses 40 are evenly distributed circumferentially around the longitudinal axis X, wherein each group comprises four mounting recesses 40 which are arranged equidistantly one next to the other. The mounting recesses 40 are configured to receive the fixing means, i.e. screws, for mounting the fan element 34 to the crankshaft 12.

In the outer band section, the fan element 34 is provided with a plurality of fan blades 38 which are evenly distributed circumferentially around the longitudinal axis X. Each fan blade 38 is designed such that, in the mounted state of the fan element 34, it is bend outwardly along the longitudinal axis X in the direction pointing from the inside 22 of the crankcase 16 to the crankshaft flange 14. In other words, each fan blade 38 is designed such that it is bend outwardly towards the front face 30 of the end cover 24. As such, each fan blade 38 comprises a projecting or protruding end 44 which is exposed and an opposing abutting end 46 via which the fan blade 38 is mounted to a base body of the fan element 34 as depicted in Fig. 3. In the shown configuration, when viewed in the rotating direction of the fan blade 38 indicated by arrow A in Fig.2, the projecting end 44 of a fan blade 38 is arranged after its abutting end 46.

The seal unit 26 further comprises a flow control element 48 which is configured to deflect and guide the fluid stream generated by and passing through the fan element 34. In the shown configuration, the flow control element 48 is arranged circumferentially around and thus radially adjacent to the fan blades 38 and extends along the longitudinal axis X. As such, the flow control element 48 has a hollow-cylindrical shape. In other words, the flow control element 48 has a sleeve-shaped design.

The flow control element 48 is configured to deflect the fluid stream generated by and passing through the fan element 34 such that it flows upstream of the fan element 34 in a flow direction which is parallel to the longitudinal axis X. In the context of the present disclosure, the term “upstream” refers to the flow direction of the flow stream in the area of the fan element 34. For doing so, the flow control element 48 extends from the fan element 34 along the longitudinal axis X in a direction pointing towards the crankshaft flange 14, i.e. towards the outside of the engine 10. As such, the flow control element 48 overlaps with at least a part of the seal 28 along the longitudinal axis X. More specifically, the flow control element 48 overlaps with at least a part of the side wall 32 of the end cover 24. Further, the flow control element 48 overlaps with the fan element 34 along the longitudinal axis X.

By such a configuration, the flow control element 48 forms a flow channel 50 in the area of the fan element 34 and the seal 28 which delimits and defines a flow passage of the fluid stream upstream of the fan element 34. The flow channel 50 is provided between the flow control element 48 and the seal 28, in particular the side wall 32 of the end cover 24. The flow control element 48 constitutes an outer side wall of the flow channel 50, wherein the side wall 32 of the end cover 24 constitutes an inner side wall of the flow channel 50.

The flow control element 48 is firmly fixed to the fan element 34 at a radially outer end of the fan element 34. Accordingly, the flow control element 48 rotates together with the fan wheel when the crankshaft 12 is driven. In the shown configuration, the flow control element 48 may be welded to the fan element 34. Alternatively, the fan element 34 and the flow control element 48 may be provided as an integral part.

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. 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.

Accordingly, a crankshaft seal unit for an internal combustion engine may be provided. The crankshaft seal unit may comprise a seal which, in a mounted state in which the crankshaft seal unit is mounted to the engine, is configured to provide sealing between a crankshaft and a crankcase of the engine. The crankshaft seal unit may further comprise a fan element which is configured to be mounted to the crankshaft in the crankcase. In other words, in a state in which the fan element is mounted to the crankcase, the fan element is disposed within the crankcase, i.e. in an inside of the crankcase in which the crankshaft is received. In the context of the present disclosure, the term “fan element” refers to a component or machine element which is configured to transform rotational movement or power into translational thrust by acting upon a fluid.

When being mounted to the crankshaft, the fan element may be configured to rotate together with the crankshaft. In other words, the fan element may be torque-transmittingly mounted to the crankshaft. As such, the fan element may be configured to act upon a fluid present around the crankshaft upon being rotated together with the crankshaft, thereby exerting a translational thrust on the fluid which may generate a fluid flow along the seal. As a result of this fluid flow, a pressure drop at an inner side of the seal, i.e. which is disposed and oriented towards the inside of the crankcase may be induced.

In the context of the present disclosure, it has been found that the amount of leakage of a fluid from the inside of the crankcase through the seal between the crankshaft and the crankcase depends on the pressure difference acting among the seal, i.e. between its inside and its outside end, and therefore on the pressure prevailing at the inner side of the seal. By being provided with the fan element which is intended and configured for being mounted to the crankshaft in the crankcase, the proposed crankshaft seal unit is equipped with a means for reducing pressure acting upon the inner side end of the seal, thereby reducing the force acting upon the fluid when entering to the inner side end of the seal. In this way, leakage of fluid from the inside of the crankcase through the seal may be reduced.

The proposed crankshaft seal unit is intended and configured for being used in an internal combustion engine, particularly large engines as being used in vessels or power plants as, for example, main or auxiliary engines. However, the present disclosure is not limited to these applications.

The proposed crankshaft seal unit may be configured such that, in the mounted state, the fan element is arranged next to the inner side of the seal, in particular along a longitudinal axis of the crankshaft. That is, when viewed in a direction along the longitudinal axis pointing from the inner side of the seal towards the inside of the crankcase, the fan element, in particular its fan blades, is/are disposed after the seal. In other words, the crankshaft seal unit may be configured such that, in the mounted state, the fan element, in particular its fan blades, faces/face the inner side of the seal. Preferably, the fan element is mounted to the crankshaft such that a gap is present between the fan element and the seal.

In a further development, the fan element may be configured to generate a pressure gradient among the fan element upon rotating with the crankshaft. Specifically, the fan element may be configured to generate the pressure gradient such that a pressure prevailing on a side of the fan element which faces the seal is smaller compared to a further pressure prevailing an opposing side of the fan element, i.e. which is arranged opposed to the first side.

Further, the fan element may be configured to, upon rotation with the crankshaft, subject the inner side of the seal to a pressure drop. In other words, when the fan element is rotationally actuated together with the crankshaft, the inner side of the seal is subjected to a pressure drop which is effected by the rotating action of the fan element. To that end, the fan element may be configured to, upon rotation with the crankshaft, generate a fluid stream which flows from the inner side of the seal through the fan element, in particular its fan blades.

Specifically, the fan element may be configured to be mounted to the crankshaft such that the longitudinal axis of the crankshaft and a longitudinal axis of the fan element, i.e. which extends through the fan elements centre of gravity, coincide. In a further development, the fan element may be configured to be mounted to a crankshaft flange. Specifically, the fan element may be configured to be mounted to an inner front end of the crankshaft flange which is oriented towards the inside of the crankcase and to which a drive shaft of the crankshaft is mounted. According to one configuration, the fan element may be provided in the form of a fan wheel. The fan wheel may be configured to be mounted around the crankshaft and around the longitudinal axis of the crankshaft.

In a further development, the crankshaft seal unit may be equipped with a flow control element. The flow control element may be configured to affect a flow direction of the fluid stream in a desired way. Accordingly, the flow control element may be configured to guide the fluid stream. More specifically, the flow control element may be configured to form a flow channel which may be arranged around the seal to guide the fluid stream from the seal to the fan element.

The flow control element may be mounted to the fan element. Further, the flow control element may have a hollow-cylindrical shape, a longitudinal axis of which may coincide with the longitudinal axis of the crankshaft.

In a further development, the seal may be a labyrinth seal. To that end, the seal may extend between the crankshaft, in particular the crankshaft flange, and the crankcase along the longitudinal axis of the crankshaft. More specifically, the seal may be provided between a side wall of the crankcase and the crankshaft, in particular the crankshaft flange. In this configuration, the side wall may have an inner front end, i.e. which is oriented towards the inside of the crankcase. The inner front end of the side wall may face the fan element, i.e. its fan blades, and may be arranged in parallel to the the fan element.

Furthermore, an internal combustion engine may be provided comprising a crankshaft seal unit as described above.

Industrial Applicability

With reference to the Figures and their accompanying description, a crankshaft seal unit for an internal combustion engine and an internal combustion engine which is equipped with such a crankshaft seal unit are suggested. The crankshaft seal unit as mentioned above is applicable in internal engines, for example, as used in vessels or power plants. The suggested crankshaft seal unit may replace conventional crankshaft seals and may serve as a replacement or retrofit part. By being provided with a fan element which is intended and configured for being mounted to a crankshaft in a crankcase, the proposed crankshaft seal unit is equipped with a means for reducing pressure acting upon an inner side end of a crankshaft seal, thereby reducing the force acting upon a fluid when entering the inner side end of the seal. In this way, compared to known configurations, leakage of fluid from the inside of the crankcase through the crankshaft seal may be reduced.