HYDRODYNAMIC GEARBOX, GEARBOX AND USE

Abstract

A hydrodynamic bearing for accommodating and supporting a rotating element includes an unloaded sliding surface, a loaded sliding surface downstream of the unloaded sliding surface, a first injection pocket arranged within the unloaded sliding surface and a second injection pocket arranged within the loaded sliding surface. A radial recess arranged within the unloaded sliding surface and the loaded sliding surface extends in a circumferential direction such as to overlap the first and second injection pockets in the circumferential direction upstream and downstream. The radial recess defines or delimits an active area of the unloaded and loaded sliding surfaces. Each of the first and second injection pockets has an axial length which is smaller than an axial extension of the active area upstream or downstream in a corresponding circumferential sliding section of the unloaded sliding surface and loaded sliding surface in which the first and second injection pockets respectively are arranged.

Claims

1.-15. (canceled)

16. A hydrodynamic bearing for a rotating element, the hydrodynamic bearing comprising: an unloaded sliding surface; a loaded sliding surface downstream of the unloaded sliding surface; a first injection pocket arranged within the unloaded sliding surface; a second injection pocket arranged within the loaded sliding surface; a radial recess arranged within both the unloaded sliding surface and the loaded sliding surface and extending in a circumferential direction such as to overlap both the first injection pocket and the second injection pocket in the circumferential direction both upstream and downstream, the radial recess defining or delimiting an active area of both the unloaded sliding surface and the loaded sliding surface, wherein each of the first and second injection pockets has an axial length which is smaller than an axial extension of the active area upstream or downstream in a corresponding circumferential sliding section of the unloaded sliding surface and loaded sliding surface in which the first and second injection pockets respectively are arranged, and wherein the radial recess provides for fluid communication between an evacuation point and the unloaded sliding surface.

17. The hydrodynamic bearing according to claim 16, wherein the active area of both the unloaded sliding surface and the loaded sliding surface is defined or delimited by providing, at the radial recess, a radial clearance which is at least factor 3 bigger than a radial clearance of the active area; and/or wherein both the first and second injection pockets are arranged and configured for providing new fluid for the hydrodynamic bearing within the active area such that an old fluid stream coming from circumferential sections further upstream is divided upstream of the respective one of the first and second injection pockets and is directed to both lateral sides; and/or wherein upstream of the first injection pocket, the active area comprises a first unloaded sliding section, preferably having a shape of a rectangular land leading to the first injection pocket; and/or wherein the first and second injection pockets are arranged and configured for axially deflecting old fluid for evacuation of the old fluid via the recess in an operational state, wherein the old fluid is squeezed by new fluid injected via the first and second injection pockets.

18. The hydrodynamic bearing according to claim 16, wherein the radial recess, especially a respective groove arranged within the radial recess, is arranged laterally on both sides of the first and second injection pockets; and/or wherein the radial recess is provided by one single coherent recess, especially by a recess extending over a whole axial length of the hydrodynamic bearing or sliding surface and exhibiting a U-shape in the circumferential direction downstream and bordering at least the unloaded sliding surface and also partly the loaded sliding surface; and/or wherein the radial recess provides for fluid communication between the evacuation point and the unloaded sliding surface, namely for/via a plurality of evacuation points on both lateral sides of the active area of the unloaded sliding surface; and/or wherein in conjunction with the radial recess, a relative position of the first injection pocket within the unloaded sliding surface defines a duplicate U-shaped arrangement of a frontal section of the radial recess encompassing a first unloaded sliding section of the unloaded sliding surface which itself encompasses the first injection pocket also in a U-shape in the circumferential direction, especially with lands extending on both lateral sides of the first injection pocket.

19. The hydrodynamic bearing according to claim 16, wherein in an axial direction the first and second injection pockets are arranged in a centered manner with respect to an absolute axial length of the hydrodynamic bearing or of the unloaded and loaded sliding surfaces, especially also arranged in a centered manner with respect to each other; and/or wherein the active area of the loaded sliding surface comprises lands arranged axially laterally of the second injection pocket to provide a continuous/continuity area between the active areas of the unloaded and loaded sliding surfaces; and/or wherein the active areas of the unloaded and loaded sliding surfaces comprise first and second lands arranged axially laterally of the first and second injection pockets.

20. The hydrodynamic bearing according to claim 16, wherein in the circumferential direction the first injection pocket is arranged downstream offset from a starting line of the unloaded sliding surface, especially with a circumferential downstream offset of at least 20?, especially with a downstream offset of maximum 60?; and/or wherein in the circumferential direction the first injection pocket is larger than the second injection pocket, especially larger about at least factor 2; and/or wherein in an axial direction the first injection pocket is shorter than the second injection pocket, especially shorter about at least factor 0.6; and/or wherein in the circumferential direction the second injection pocket is arranged at a starting line of the loaded sliding surface, especially arranged in parallel thereto.

21. The hydrodynamic bearing according to claim 16, wherein the evacuation point is provided at/within the radial recess, especially in a section downstream of the first injection pocket, especially within a groove arranged within the radial recess; and/or wherein the radial recess accommodates a groove extending in the circumferential direction, especially two grooves, wherein the evacuation point is provided within the groove; and/or wherein the radial recess exhibits at least two areas or sections having a different radial clearance, wherein the section having a bigger radial clearance is preferably provided by the groove; and/or wherein evacuation of fluid is exclusively carried out on lateral border areas requiring axial deflection of the fluid.

22. The hydrodynamic bearing according to claim 16, wherein the radial recess defines a starting line of the unloaded sliding surface; and/or wherein the radial recess provides for a frontal section upstream of the first injection pocket, the frontal section preferably having a rectangular shape, the frontal section preferably providing for a U-shaped configuration of the active area encompassing the first injection pocket; and/or wherein the radial recess extends from the unloaded sliding surface to the loaded sliding surface over a circumferential length of at least 180?, preferably of at least 190? or 200?.

23. The hydrodynamic bearing according to claim 16, wherein the hydrodynamic bearing comprises exactly two injection pockets only, one of the two injection pockets being said first injection pocket and the other one of the two injection pockets being said second injection pocket, with the first and second injection pockets in direct fluid communication with the active areas of the unloaded and loaded sliding surfaces and thus with a rotating element, both the first and second injection pockets preferably having a rectangular shape; and/or wherein the first and second injection pockets of the hydrodynamic bearing are arranged with respect to each other and with respect to the radial recess in such a manner that a bearing's fluid pressure profile has a minimized ratio of maximum pressure to specific pressure, especially with the radial recess circumferentially overlapping the second injection pocket and lands being arranged at both axial ends of the second injection pocket.

24. The hydrodynamic bearing according to claim 16, wherein the radial recess extends in the circumferential direction on both border areas of the hydrodynamic bearing of both the unloaded sliding surface and the loaded sliding surface, preferably even further than a circumference position at least approximately corresponding to half the circumference of the bearing.

25. The hydrodynamic bearing according to claim 16, wherein between the first injection pocket and the second injection pocket, in the circumferential direction, the hydrodynamic bearing exhibits a continuous/continuity area.

26. The hydrodynamic bearing according to claim 16, wherein the unloaded and loaded sliding surfaces, starting from a starting line of the unloaded sliding surface in the circumferential direction, exhibit an axial length which increases at least at three circumferential points; and/or wherein an area of reduced activity of the unloaded sliding surface, starting from the starting line of the unloaded sliding surface in the circumferential direction, exhibits an axial length which decreases at least at three circumferential points.

27. The hydrodynamic bearing according to claim 16, wherein the hydrodynamic bearing exhibits a plurality of sliding surfaces at least comprising the unloaded sliding surface and the loaded sliding surface, the hydrodynamic bearing further comprising a bearing shell designed to exhibit the unloaded sliding surface and the loaded sliding surface wherein the hydrodynamic bearing exhibits a plurality of areas of pressure on both the unloaded sliding surface and the loaded sliding surface, wherein activity of any of the plurality of areas of pressure preferably is defined by a radial position/elevation/height of respective sections of the unloaded sliding surface and the loaded sliding surface.

28. The hydrodynamic bearing according to claim 16, wherein in a top view on the unloaded and loaded sliding surfaces, the active area of the unloaded sliding surface is T-shaped having a first substantially rectangular sliding section and a second substantially rectangular sliding section having a greater axial length and circumferential extension than the first sliding section, wherein the first injection pocket is arranged in the first sliding section, and the active area of the loaded sliding surface is T-shaped having a first substantially rectangular sliding section and a second substantially rectangular sliding section having a greater axial length and circumferential extension than the first sliding section of the loaded sliding surface, wherein the second injection pocket is arranged in the first sliding section of the loaded sliding surface.

29. The hydrodynamic bearing according to claim 16 for use in a rotating machine, especially in a gearbox, especially in a turbo gearbox, wherein the hydrodynamic bearing accommodates and supports a rotating element, especially a shaft of a power train, wherein the hydrodynamic bearing is coupled to a pressure line for fluid injection.

30. A gearbox, comprising a hydrodynamic bearing as set forth in claim 16, wherein the gearbox preferably is configured for a turbo application requiring at least 60 m/s of journal velocity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In the following, the invention is explained in more detail with reference to the attached drawings, using preferred design examples. The word figure is abbreviated in the drawings as Fig. The drawings show in

[0072] FIG. 1A, 1B, 1C, 1D, 1E in different views a hydrodynamic bearing according to a preferred design example of the present invention;

[0073] FIG. 2A, 2B, 2C in three schematic tops views the sliding surfaces of a hydrodynamic bearing according to design examples of the invention, wherein the complete circumference is illustrated in the top view, respectively;

[0074] FIG. 3A, 3B a schematic illustration of a pressure profile provided by a hydrodynamic bearing according design examples of the invention, respectively;

[0075] FIG. 4 a schematic illustration of a gearbox comprising at least one hydrodynamic bearing according to design examples of the invention;

[0076] FIG. 5A, 5B in different perspective views in schematic illustration the fluid flow path in hydrodynamic bearings according to preferred design examples of the present invention.

DETAILED DESCRIPTION OF DESIGN EXAMPLES

[0077] The described design examples are only examples which can be modified and/or supplemented in many ways within the scope of the claims. Each feature described for a/the specific design example can be used independently or in combination with other features in any other design example. Each feature described for the design example of a particular claim category can also be used in a corresponding way in a design example of another claim category. First, the elements and items shown in the figures are described in general, and a specific description is provided in context with individual figures.

[0078] A hydrodynamic bearing 10, especially plain bearing or journal bearing, accommodates and supports a rotating element 1 (shaft), e.g. in a gearbox 3, especially in turbo applications. Fluid F (especially oil) is supplied to the bearing via at least one pressure line/pipe 5 for fluid injection. In particular, the hydrodynamic bearing 10 may exhibit at least two shells, e.g. a first bearing shell 10.1 and a second bearing shell 10.2. In circumferential direction y, an unloaded sliding surface 10a is arranged upstream of a loaded sliding surface 10b (i.e., a surface facing the force at full load). In particular, the unloaded sliding surface 10a and the loaded sliding surface 10b may each encompass half a circumference, i.e. ca. 180?. A first injection pocket 11 is provided in the unloaded surface, and a second injection pocket 12 is provided in the loaded surface. A radial recess 13 is provided upstream of the first injection pocket 11 and laterally to/from the first and second injection pockets 11, 12, the radial recess 13 extending in circumferential direction and being arranged laterally of the active area A1 of the unloaded sliding surface and also partly laterally of the active area A2 of the loaded sliding surface. The at least one radial recess 13 provides for a corner/border area Ax which mainly extends along the unloaded sliding surface, and the at least one radial recess 13 also provides for a frontal section Ax0 of the corner/border area, the frontal section Ax0 being arranged on the frontal/upstream side of the active area A1 of the unloaded sliding surface, i.e., also on the frontal/upstream side of the first injection pocket 11. Thus, the active area A1 only begins at/with a circumferential offset YA1 further downstream of a/the starting line Y1 of the unloaded sliding surface, and the first injection pocket 11 only begins at/with a circumferential offset Y11 further downstream of the starting line Y1 of the unloaded sliding surface.

[0079] Fluid evacuation points P can be provided within the radial recess 13, especially within its sections extending in circumferential direction laterally of the active area A1 of the unloaded sliding surface.

[0080] In the following, specific regions/sections of the sliding surfaces 10a, 10b are described in more detail: The active area A1 of the unloaded sliding surface 10a exhibits a first unloaded sliding section A1a (rectangular land leading to the first injection pocket) and a second unloaded sliding section A1b arranged downstream of the first unloaded sliding section A1a and downstream of the first injection pocket 11, wherein first lands A1c laterally extending along the first injection pocket 11 connect the first unloaded sliding section A1a with/to the second unloaded sliding section A1b. The axial extension A1x of the first unloaded sliding section A1a is greater than the axial extension of the first injection pocket 11, but considerably smaller than the axial extension A1x of the second unloaded sliding section A1b.

[0081] The active area A2 of the loaded sliding surface 10b exhibits a first loaded sliding section A2a and a second loaded sliding section A2b arranged downstream of the first loaded sliding section A2a, wherein both loaded sliding sections A2a, A2b are arranged downstream of the second injection pocket 12, wherein second lands A2c laterally extending along the second injection pocket 12 connect the second unloaded sliding section A1b with/to the first loaded sliding section A2a. The axial extension A2x of the first loaded sliding section A2a is greater than the axial extension of the second injection pocket 12, but considerably smaller than the axial extension A2x of the second loaded sliding section A2b.

[0082] A continuity area Ay extending from first to second injection pockets 11, 12 (without any injection pocket resp. evacuation point being arranged therein) also circumferentially extends also beyond the second injection pocket 12, namely via second lands A2c, which is illustrated in FIG. 2B (no interruption of that continuity area Ay even up to the end of the loaded sliding surface 10b resp. its active area A2).

[0083] The first injection pocket 11 preferably ends/terminates at a circumferential positions corresponding to the transition from first to second unloaded sliding section A1a, A1b (namely corresponding to circumferential position y2). In contrast to the configuration of the unloaded sliding surface A1, the loaded sliding surface A2 exhibits a continuity area Ay2a within the first loaded sliding section A2a downstream of the second injection pocket 12. I.e., the second injection pocket 12 preferably ends/terminates at a circumferential positions well upstream of the transition from first to second loaded sliding section A2a, A2b (namely upstream to circumferential position y3).

[0084] The pressure profile provided by the configuration described herein is designated by reference sign PP, wherein PPL reference sign designates a low pressure zone.

[0085] To sum up, the relative position XY11 of the first injection pocket 11 within the active area A1 of the unloaded surface 10a can be described/designates as U-shaped arrangement (in circumferential direction), wherein both a U-shaped arrangement of the frontal section of the radial recess 13 encompassing the first unloaded sliding section Ala of the unloaded sliding surface and also a U-shaped arrangement of the first unloaded sliding section A1a encompassing the first injection pocket 11 are provided, wherein lands A1c extend on both lateral sides of the first injection pocket.

[0086] Reference sign Y2 designates the starting line of the loaded sliding surface A2, wherein the second injection pocket 12 is arranged at that starting line Y2 in parallel to/with that starting line Y2.

[0087] The axial length of first and second lands A1c, A2c is designated by reference sign ?x, illustrating an axial offset resp. an axial continuity area/section without any injection pocket or evacuation point.

[0088] Reference sign YY designates a complete circumference/cycle (length according to 360? of inner lateral surface/area), and p designates a/the film/fluid pressure, especially in [bar], and r designates the radial direction, x designates the axial (longitudinal) direction, and y designates the circumferential direction/sliding direction, especially in [?] of 360?. Reference signs y1, y2, y3 each designate a circumferential point resp. circumference position of an increasing axial length (resp. broadness/width) of the active area of the sliding surface(s).

[0089] In the following, specific aspects of the present invention are described in more detail by individually referring to the figures.

[0090] FIG. 1 show a hydrodynamic bearing 10 exhibiting two half shells 10.1, 10.2, namely a first half shell 10.1 (especially the half shell being the unloaded shell in operational state) providing for the unloaded sliding surface 10a, and a second half shell 10.2 (especially the half shell being the loaded shell in operational state) providing for the loaded sliding surface 10b. Lateral recesses 13 circumferentially extend along the first injection pocket 11, and the first half shell 10.1 exhibits a recess section 13 which is arranged upstream of the first injection pocket 11, providing for a frontal section Ax0 of reduced activity. The first half shell 10.1 also provides for several fluid evacuation points P which lead to each of the two circumferentially extending sections of the recess 13. In particular, the circumferential sections of the recess 13 being arranged in the first half shell 10.1 may have a greater depth (especially provided by a groove or corrugation) than the further sections of the recess 13. This specific configuration of the recess 13 extending laterally from the active unloaded area A1 can be designed depending on each individual application, especially depending on desired fluid flow rates or the like (e.g. also depending on the total axial length of the bearing).

[0091] In particular, FIG. 1A illustrates the relative circumferential position of the first injection pocket 11 with respect to the first and second unloaded sliding sections A1a, A1b.

[0092] In particular, FIG. 1B illustrates the relative circumferential position of the second injection pocket 12 with respect to the starting line Y2 of the loaded sliding surface 10b and with respect to the recesses 13 circumferentially overlapping/extending in the loaded sliding surface area.

[0093] In particular, by referring to the total axial extension XX (complete axial length) of the bearing, FIG. 1C illustrates the following axial extensions x1, x2, x3, x4, A1x of respective unloaded surface sections, especially according to the following factors (at least approximately): 0.1*XX<x1<0.3*XX; 0.1*XX<x2<0.3*XX; 0.15*XX<A1x<0.45*XX; 0.3*XX<x3<0.45*XX; 0.1*XX<x4<0.4*XX; (excluding x1 and x2 being simultaneously at their maximum/minimum value). Alternatively or in addition, the relative size can also be dependent on the axial extension x4 of the first injection pocket 11, especially according to the following factors (at least approximately): 0.25*x4<x1<3*x4 (especially about factor 1.5*x4); 0.25*x4<x2<3*x4 (especially about factor 1.5*x4); 1*x4<x3<4.5*x4 (especially about factor 2.5*x4); 1*x4<A1x<2*x4 (especially about factor 1.5*x4). The skilled person may choose the preferred reference to XX and/or to x4.

[0094] In particular, by referring to the total axial extension XX (complete axial length) of the bearing, FIG. 1D illustrates the following axial extensions x5, x6, x7, x8, x9 of respective unloaded and loaded surface sections, especially according to the following factors (at least approximately): 0.3*XX<x5<0.6*XX; 0.2*XX<x6<0.35*XX; 0.1*XX<x7<0.3*XX;

[0095] The axial extensions x8 and x9 can be dependent on the axial extension x7 according to the following factors (at least approximately): 0.5*x7<x8<0.7*x7; 0.15*x7<x9<0.25*x7;

[0096] Alternatively or in addition, the relative size can also be dependent on the axial extension x5 of the second injection pocket 12, especially according to the following factors (at least approximately): 0.5*x5<x6<1*x5 (especially about factor 0.75*x5); 0.2*x5<x7<1.0*x5 (especially about factor 0.5*x5); 0.2*x5<x8<0.5*x5 (especially about factor 0.3*x5); 0.05*x5<x9<0.2*x5 (especially about factor 0.1*x5). The skilled person may choose the preferred reference to XX and/or to x5.

[0097] As shown in FIG. 1D, reference sign y12 designates the circumferential extension of second injection pocket 12. Preferably, the ratio of axial length x5 to circumferential extension y12 of the second injection pocket 12 (ratio x5:y12) is within the range of 6 to 15, especially about 10.

[0098] As shown in FIG. 1E, in each shell 10.1, 10.2, optionally, an eccentricity (e) of the center of the sliding surface can be provided, especially in order to define the unloaded and loaded sliding sections more clearly and do allow for more distinguished fluid flow of both pressurized new fluid and used fluid which should be evacuated via evacuation points P. Eccentricity, and thus, diameter (d) can specifically be designed with respect to the diameter of the rotating element and/or operation conditions and/or required performance (especially stiffness).

[0099] FIG. 2 further illustrate relative positions and dimensions of surface sections, in schematic manner. In FIG. 2A, 2B, a/the reduced active area is illustrated by blank areas, wherein the active areas of the unloaded and loaded sliding surfaces are illustrated by dotted areas.

[0100] In particular, FIG. 2A shows the recess 13 (double U-shape recess with two pairs of opposed flanks resp. circumferential sections), wherein the recess 13 extends both laterally (thereby overlapping the second starting line Y2) and axially, providing for a/the frontal (quite passive) section Ax0 and also providing for a/the triple cascade of increasing active area being enlarged (in its axial extension) at three circumferential points y1, y2, y3.

[0101] In particular, FIG. 2B illustrates the relative positions of first and second lands A1c, A2c laterally from respective injection pocket 11, 12, and also, the circumferential offset YA1, Y11 is described by referring to the starting lines Y1, Y2 and also by referring to the circumference position of increasing length (resp. broadness/width) of the active area of the unloaded and loaded sliding surfaces.

[0102] The reduced active area Ax of the unloaded sliding surface 10a also allows for reduced power losses. The reduced active area Ax of the loaded sliding surface 10b is arranged in a region of low pressure PPL.

[0103] The present invention is also based on the following concept and findings: At the first injection pocket 11, a first central inward flow of fluid is supplied directly to the active area of the unloaded surface, and at the second injection pocket 12, a second central inward flow of fluid is supplied directly to the active area of the loaded surface, wherein both injection pockets 11, 12 are arranged centrally (with respect to the axial direction x), and wherein both injection pockets 11, 12 are (fluidically) coupled to active area sections further upstream, especially via lands A1c. A2c. The first injection pocket 11 is arranged with circumferential offset YA1 in a distance to the beginning (starting line) of the unloaded sliding surface, which also allows for preventing cavitation especially in the middle of the unloaded sliding surface. The first injection pocket 11 is (relatively) large in circumferential sliding direction y, which also allows for good (relatively large) fluid flow rates. The first injection pocket 11 is (relatively) short in axial direction x, which also allows for a design having a (relatively) large area Ax of reduced activity. The second injection pocket 12 is arranged directly at the beginning (starting line) of the loaded sliding surface, which also allows for maximizing the active area and for reducing maximum temperature and maximum pressure. The second injection pocket 12 is (relatively) short in circumferential sliding direction y, which also allows for maximizing active area. The second injection pocket 12 is (relatively) long in axial direction x, which also allows for good lubrication characteristics. The lands A1c, A2c also allow for fluid communication between the unloaded and loaded sliding surfaces and may enhance dynamic stability. Also, these lands A1c, A2c can ensure continuity of bearing profile between the unloaded and loaded sliding surfaces.

[0104] In particular, FIG. 2C illustrates an alternative contour of the border line bordering the active areas A1, A2a; i.e., the rectangular shape illustrated in FIG. 2A, 2B can also be made round such that any discrete edges are rounded. Departing from the embodiment shown in FIG. 2A, 2B, the skilled person is able to provide such design alternatives for specific applications, in order to further improve efficiency and fluid flow. It should be noted that the radius resp. the curvatures of the border line is/are illustrated in an excessively exaggerated manner in FIG. 2C, in order to facilitate comprehension of any such design alternatives resp. variations in geometry of each of the active area sections.

[0105] FIG. 3 show an advantageous pressure profile PP exhibiting low pressure zones PPL and having a parabolic shape with a peak residing approximately at half the circumference of the loaded sliding surface, approximately a little more than 270?.

[0106] In particular, FIG. 3A shows that the main pressure peak increases and decreases in quite homogeneous manner both in circumferential direction and in axial direction.

[0107] In particular, FIG. 3B shows a first increase (relatively small pressure wave) at about 90? to 180?, and at a circumferential point between ca. 270? and 300?, the main pressure peak (corresponding to pressure in loaded sliding surface area) provides for an advantageous parabolic shape of the pressure profile.

[0108] FIG. 4 illustrates further components of a gearbox arrangement 3 exhibiting at least one hydrodynamic bearing 10 according to the present invention, wherein the rotating element 1 is part of a power train especially in turbo applications.

[0109] Pressure line 5 may provide for fluid for both injection pockets 11, 12 or individually for each of first and second injection pockets (wherein several pressure lines 5 may be provided); also, fluid evacuated from evacuation points P can be evacuated via such a line 5, individually or in conjunction with provision of fluid to injection pockets 11, 12. Thus, pressure line 5 (or evacuation line) shown in FIG. 4 should be considered as schematic example only; the skilled person can choose an appropriate design for provision of pressure/fluid and evacuation of fluid via several lines according to each individual application.

[0110] FIG. 5 illustrate the flow of fluid F and the active surface area having minimal radial clearances as well as the non-active surface areas (resp. the at least one radial recess) having relatively high radial clearance (especially at least factor 3 and up to e.g. factor 5 bigger than the low/minor clearance of the active area). At the outer shell surface, there is at least one canal or groove for fresh oil supply. Deep grooves 13a being arranged within radial recess 13 are provided for radial evacuation of used fluid, communicating with evacuation points P.

[0111] In particular, FIG. 5A shows pressurized new fluid F being injected at the first injection pocket 11 in order to flow along active area section A1b, and old fluid being evacuated via inactive border areas Ax and via grooves 13a. In particular, the circumferential position of the first injection pocket within the first (half) shell 10.1 is preferably within the range of 40-60?, preferably at about 50? (about 25-30% of 180? or of the circumferential extension of the unloaded shell). Thus, apart from area A1a, that mainly inactive circumferential section (of about 10-15% of 360? circumference) allows for self-adjustment and good efficiency and provision of new fluid at a favorable relative position. The dotted line arrows indicate hot and used oil coming from the loaded sliding surface is directed to the grooves 13a at the beginning of the unloaded sliding surface resp. unloaded section of the shell. Continuous line arrows: Fresh and new oil supplied via the first injection pocket is provided to the sliding surface of the unloaded sliding surface.

[0112] In particular, FIG. 5B shows pressurized new fluid F being injected at the second injection pocket 12 in order to flow along active area section A2a, A2b, and old fluid being evacuated via inactive border areas Ax and via grooves 13a (reflow). The dotted line arrows indicate hot and used resp. old oil coming from the unloaded sliding surface resp. half shell is directed to the grooves 13a at the end of the unloaded sliding section. The oil is ejected/evacuated radially from the grooves through the holes (evacuation points). Continuous line arrows: Fresh and new oil supplied via the second injection pocket is provided to the sliding surface of loaded sliding surface resp. half shell. This manner of oil injection also helps pushing the used oil into the grooves. A small fraction of that new oil may flow to the non active surfaces and may create a kind of small backflow back to the evacuation grooves arranged at the unloaded sliding section (cf. dashed line arrows).

[0113] While several aspects of the hydrodynamic bearing are shown in the accompanying figures and described in detail hereinabove, other aspects will be apparent to, and readily made by, those skilled in the art without departing from the scope and spirit of the disclosure. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. The invention described hereinabove is defined by the appended claims and all changes to the invention that fall within the meaning and range of equivalency of the claims are to be embraced within their scope.

REFERENCE LIST

[0114] 1 rotating element [0115] 3 gearbox [0116] 5 pressure line/pipe for fluid injection [0117] 10 hydrodynamic bearing, especially plain bearing or journal bearing [0118] 10.1 first bearing shell, especially arranged below the rotating element [0119] 10.2 second bearing shell, especially arranged above the rotating element [0120] 11 (first) injection pocket in unloaded surface, especially in first bearing shell [0121] 12 (second) injection pocket in loaded surface, especially in second bearing shell [0122] 13 radial recess extending in circumferential direction and being arranged laterally of the active area of the sliding surface, optionally combined with evacuation points [0123] 13a groove [0124] 10a unloaded sliding surface [0125] 10b loaded sliding surface (facing the force at full load) [0126] A1 active area of unloaded sliding surface [0127] A1a first unloaded sliding section [0128] A1b second unloaded sliding section [0129] A1c first lands [0130] A1x axial extension of first unloaded sliding section [0131] A1x axial extension of second unloaded sliding section [0132] A2 active area of loaded sliding surface [0133] A2a first loaded sliding section [0134] A2b second loaded sliding section [0135] A2c second lands [0136] A2x axial extension of first loaded sliding section [0137] A2x axial extension of second loaded sliding section [0138] Ax corner/border area especially of the unloaded sliding surface [0139] Ax0 frontal section of the corner/border area [0140] Ay continuity area without any evacuation point or injection pocket [0141] Ay2a continuity area of first loaded sliding section downstream of second injection pocket [0142] d diameter [0143] e eccentricity [0144] F fluid (resp. fluid flow direction) [0145] P evacuation point [0146] PP pressure profile [0147] PPL low pressure zone [0148] XX total axial extension (complete axial length) [0149] XY11 relative position of first injection pocket within unloaded surface, especially in U-shaped arrangement [0150] YA1 circumferential offset further downstream of active unloaded area from starting line [0151] Y11 circumferential offset further downstream of injection pocket within unloaded surface [0152] Y1 starting line of the unloaded sliding surface [0153] Y2 starting line of the loaded sliding surface [0154] YY complete circumference/cycle (length according to 360? of inner lateral surface/area) [0155] p film/fluid pressure, especially in [bar] [0156] r radial direction [0157] x axial (longitudinal) direction [0158] x1, x2, x3, x4 axial extension of respective unloaded surface section shown in FIG. 1C [0159] x5, x6, x7, x8, x9 axial extension of respective un-/loaded section shown in FIG. 1D [0160] ?x axial offset resp. axial continuity area/section without any injection pocket or evacuation point [0161] y circumferential direction/sliding direction, especially in [?] of 360? [0162] y1, y2, y3 circumferential point(s) resp. circumference position of increasing length (resp. broadness/width) of sliding surface [0163] y12 circumferential extension of second injection pocket