System for reducing tooth power losses in gearboxes

Abstract

The present invention provides a system for reducing tooth power losses in a gearbox (1). It comprises two intermeshing gears (11, 12), each mounted on a rotating shaft (13, 14) supported by bearings (15, 16), and mounted in a housing (10). It includes two vertical plates (2) installed in the housing (10), one on each side of the gears (11, 12), between the bearings (15, 16) and the gears (11, 12). The vertical plates (2) comprise one or more internal shields configured to separate the oil flows in the housing (10), mounted on the side of the vertical plates (2) oriented towards the gears (11, 12). The internal shields comprise anti-recirculation plates (230, 240). At least one of the anti-recirculation plates (230, 240) comprises one or more vertical fins (233) to impede the axial flow of the air and oil mixture.

Description

[Technical field]

[0001] The present invention relates to gearboxes (also called transmissions) with mechanical gears, and more particularly to tooth power losses in such gearboxes. [Background technology]

[0002] As known in the art, a gear mechanism is usually mounted in a housing (or case or casing) with at least two gears, i.e., a first gear and a second gear, which are toothed components. The two gears are mounted on a shaft that rotates in bearings mounted in the housing. The teeth of the gears engage with each other, so that the rotation of one of the gears rotates the other gear. The housing forms the case of a transmission mechanism, for example used for driving a generator by a turbine. The housing and the gear mechanism fitted in the housing form a so-called gear box. Gear boxes are typically used to convert the torque and speed from one rotating machine (e.g. a rotating power source) to a torque and speed suitable for another rotating machine or device.

[0003] The invention more particularly relates to turbo gearboxes, i.e. high speed (in particular characterised by a pitch line speed in the range of 60 m / s to 180 m / s) transmission mechanisms.

[0004] Converting torque and speed does result in power losses, which manufacturers strive to minimize. The present invention more specifically focuses on teeth power losses (hereinafter "TPL"), which occur especially in turbo gearboxes. TPL can be derived from: - Friction in the gearbox, especially between multiple gears, - pumping effect resulting from an inadequate amount of lubricant being used to lubricate the meshing areas of multiple gears; -Windage, which comes from the rotational speed of the gears that causes the surrounding fluid to move. - Improperly oriented oil spurts or excessive amounts of oil spurting.

[0005] To reduce the TPL, various solutions have been proposed by manufacturers. Some solutions are based on a vacuum, for example a partial vacuum, created in the housing of the mechanical gears to reduce the aerodynamic losses. Other solutions are based on a closed gear shroud to reduce the windage losses. Other solutions are based on systems focused on the cooling of the gears. In fact, it is known that the heat induced in the meshing area, where the teeth of the gears engage during operation, can be dissipated mainly by the lubricant (or lubricant), which is at the same time used to lubricate the area. Increasing the flow of lubricant in this area, on the one hand, makes the area cooler, but on the other hand, undesirably, significantly increases the power losses. For this reason, manufacturers have proposed additional cooling devices that preserve the efficiency of the system while keeping the flow of lubricant at reasonable values, i.e. without increasing the power losses. Cooling devices known in the art include, for example, cooling ducts arranged to cool an enclosure wall surrounding the gears. However, such a solution makes maintenance operations more complex and difficult, since it prevents easy access to the different parts inside the gearbox.

[0006] US Patent Application Publication No. 2019 / 195335 discloses a system for reducing TPL in a gearbox, comprising the features recited in the preamble of claim 1.

[0007] US Patent Application Publication No. 2020 / 132183 discloses a gearbox having intermeshing gears, but with an internal shield that covers a portion of the gears within the gearbox housing.

[0008] US 2018 / 313443 discloses a cylindrical gearing having two intermeshing gears, each with an axle supported in both axial directions within a respective plate, with a shield disposed between the plates and closely spaced from an associated gear surrounding a peripheral portion of the gear.

[0009] Thus, the solutions known so far are usually of a complex design, for which reason there is still a need for simpler and more efficient solutions, in particular so as not to complicate maintenance operations. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] US Patent Application Publication No. 2019 / 195335 [Patent Document 2] US Patent Application Publication No. 2020 / 132183 [Patent Document 3] US Patent Application Publication No. 2018 / 313443 Summary of the Invention [Problem to be solved by the invention]

[0011] It is an object of the present invention to provide a simple and efficient system for reducing TPL in a gearbox. [Means for solving the problem]

[0012] The above object is achieved on the basis of the solutions set forth in the independent claims. Further advantageous embodiments are suggested in the dependent claims.

[0013] The present invention therefore relates to a system for reducing TPL in a gearbox. The system comprises a set of two independent vertical plates adapted to be mounted in the gearbox housing to separate or isolate a first oil flow used to cool and / or lubricate the teeth of the gears of the gearbox from a second oil flow used to cool and / or lubricate the hydrodynamic bearings supporting the shaft of the gearbox. The gears are mounted or fixed to said shaft. Each vertical plate is mounted laterally or transversely (with respect to the axial direction of the shaft) between the gears of the gearbox and the bearings supporting the shaft to which the gears are fixed, the gears being sandwiched between the two vertical plates. The plates are referred to as "vertical plates" because they are mounted substantially perpendicular to the shaft. Preferably, the lateral spacing between the gears and the vertical plates is defined within the range of 10 mm to 40 mm to allow axial displacement, if required.

[0014] The invention also relates to a gearbox equipped with said system for reducing the TPL. As is known in the art, the gearbox comprises at least two meshing gears (or gears which mesh together), each of which is mounted on the rotating shaft for rotation about its central axis of rotation, and each rotating shaft is thus preferably mounted for rotation about its central axis of rotation in bearings supported by the gearbox housing.

[0015] Thus, the set of vertical plates comprises at least two vertical plates, each of which is adapted to be removably installed inside the housing between a bearing supporting a rotating shaft and a number of gears, with one vertical plate on each side of the gears, so that the gears are sandwiched between the vertical plates. The vertical plates are independent of each other, so that they can be installed one after the other in the housing, i.e., they do not use any secure fastening means to fasten them, such as welding. This has the advantage that the system according to the invention can be assembled and disassembled in an existing gearbox. In the present invention, each vertical plate comprises two openings, each of which is fitted to one of the rotating shafts.

[0016] In particular, the vertical plate according to the invention comprises a set of shields for isolating the oil flow within the gearbox housing, namely: One or more external shields for separating a first oil flow arranged to cool and / or lubricate the gears from a second oil flow arranged to cool and / or lubricate the bearings are provided, which are attached to the side of the vertical plate 2 oriented towards the outside of the housing 10, i.e. in the space between the vertical plate 2 and the wall of the housing 10. The gear cooling oil is limited or prevented from recirculating by the rotation of the gears by one or more internal shields. This oil flow corresponds more precisely to a flow or flow of a mixture of air and oil. The internal shields are attached to the side of the vertical plate 2 oriented towards the gears 11, 12, i.e. in the space between the two vertical plates 2.

[0017] Preferably, each vertical plate comprises or is formed from a lower plate and an upper plate, which are arranged to be mounted or removed vertically one on the other to form said vertical plate. Preferably, said openings are formed from an edge belonging to the lower plate and another edge belonging to the upper plate, allowing the lower plate and the upper plate to be assembled around an axis of rotation, such that said edge and said other edge follow the circumference of the axis of rotation and surround said axis. Indeed, according to the invention, each vertical plate is arranged to be mounted inside said housing, with two openings fitting around each axis of rotation.

[0018] Preferably, each vertical plate comprises, for each bearing, the external shield for separating the first oil flow from the second oil flow. The external shield is configured to surround the upper part of the bearing, thus being configured like a kind of fender or hood, to guide the second oil flow towards a receptacle configured to collect the second oil flow. Preferably, the external shield comprises a first part attached to the upper plate and a second part attached to the lower plate. Preferably, the first part and the second part are a curved plate and a flat plate. Preferably, the second part comprises two secondary plates, for example rectangular plates, and is oriented, for example according to the length of the rectangular plates, towards the bottom of the lower plate (for example towards the receptacle). In this case, the first part of the external shield surrounds the upper part of the bearing and is fitted between the two secondary plates (i.e. at the ends located on each side of the bearing). For this purpose, the secondary plate forms an extension of the first part of the shield on the lower plate, which extension extends towards the bottom of the lower plate. Each of the outer shields (one for each bearing supporting the rotating shaft) is therefore configured to collect the second oil flow scattered during the operation of the bearings of the gearbox and to guide it towards the bottom of the gearbox, i.e. towards the receptacle. In the present invention, each point of one of the secondary plates is spaced from a point of the other secondary plate by a distance greater than the diameter of the bearing it surrounds, allowing easy installation of the lower plate in the housing. The advantage provided by the above technical structure is that oil droplets of the second oil flow can reach the inner wall of the outer shield during the operation of the gearbox (i.e. the shield wall is oriented towards the bearing, i.e. the normal vector of its surface is directed towards the bearing) and flow along said wall towards the receptacle by gravity. Additionally, the vertical plate may include a number of chocks attached to the sides of the vertical plate including the outer shield and configured to abut against the side walls of the housing to act as stops for the vertical plate.

[0019] The internal shield for preventing recirculation preferably includes a recirculation prevention plate, which is configured to prevent or limit the recirculation of the cooling oil of the first oil flow. The recirculation prevention plate is arranged inside the housing, behind (according to the direction of rotation of the gears) the spray area located on the outer surface of the gears, and is defined by a tooth cooling system arranged inside the housing. The recirculation prevention plate is configured to prevent the air / oil mixture from being swept by the rotation of the gears towards the meshing area (i.e. being directed towards the meshing area following a substantially circular, curved path), the air / oil mixture being generated by the injection in the spray area and by the cooling nozzles of the cooling system, the latter cooling oil being directed towards the outer surface of the gears. In particular, the recirculation prevention plate is configured to be attached to at least one of the vertical plates. Other attachment means can be used in cooperation with the attachment to the vertical plates, or alternatively, fastening means, such as screws, can be used to attach the recirculation prevention plate directly to the housing, for example. The system according to the invention comprises at least two anti-recirculation plates, preferably one for each gear of the gearbox. Preferably, each anti-recirculation plate comprises a first end adapted to be oriented towards the gear and a second opposite end adapted to be oriented towards the housing. The first end has an edge substantially parallel to the axis of rotation and has a length extending along the width, preferably the entire width, of the gear. The edge is located close to the circumference of the gear, whereas the second end is located close to the wall of the housing and preferably follows the geometric shape of said wall, for example resting on said wall. The edge of the second end extends along said wall of the housing, but preferably with a length equal to said width of the gear. Preferably, each anti-recirculation plate is attached to at least one vertical plate, preferably to both vertical plates, and in particular defines a plane substantially perpendicular to the vertical plates.Preferably, each anti-recirculation plate is slidably mounted relative to the vertical plate to allow adjustment of the space separating the anti-recirculation plate from the gears (i.e. from the outer surface of the gears to said first end). Advantageously, the anti-recirculation plate defines two distinct volumes within the gear housing, a first volume located above the anti-recirculation plate and the gears and a second volume located below the anti-recirculation plate and the gears, whereby the mixture of air and oil generated by the cooling system in the second volume (and therefore the corresponding flow thereof) is at least partially prevented by the anti-recirculation plate from reaching the first volume.

[0020] Preferably, the cooling system according to the invention comprises one or more cooling nozzles arranged below the gears and configured to direct a flow of cooling oil towards the outer surfaces of the gears, in particular at least one cooling nozzle directing a first flow of cooling oil towards one of the gears and at least one cooling nozzle directing a second flow of cooling oil towards the other of the gears, each cooling nozzle being configured to jet said cooling oil onto the outer surface of the corresponding gear. Preferably, the angle between the direction (or orientation) of the jet (or jet) of cooling oil at the outlet of the cooling nozzle and the outer surface of the gear cooled by said jet of cooling oil is between 90° (i.e. the nozzle jet, more specifically said direction is radial to the outer surface of the gear) and 180° (i.e. said direction is tangential to the outer surface). In particular, said angle is defined as an angle made up of two lines, starting from a common point which is the intersection of said directions or orientations when extended to cut the outer surface of the gears, one of which is defined by said direction or orientation when extended to said common point; the other line, starting from said common point, is extended in the direction of rotation of the gears as a tangent to the outer surface of the gears at said common point. And said angle is included in the present invention in the range [90°, 180°]. In the present invention, said cooling nozzle is located behind the meshing area, taking into account the direction of rotation of the gears, and is usually located below the gears. Thus, the cooling oil splashed by the rotation of the gears is prevented from reaching the first volume and falls by gravity towards the oil receptacle. Preferably, the cooling system comprises at least one additional nozzle, also called lubrication nozzle, which is provided for cooling and / or lubrication of the meshing area, i.e. configured to have an oil jet directed towards the engagement of the teeth of the gears. The flow of oil used for the cooling / lubrication is then controlled by a feedback loop that is a function of the temperature within the housing, or the lubrication nozzles may be part of a separate lubrication system that cooperates with the cooling system and is controlled by the feedback loop.

[0021] Independently, a further system for reducing tooth power losses in a gearbox is provided. The system comprises at least two meshing gears, each mounted on a rotating shaft supported by bearings, and mounted in a housing. Two vertical plates, one on each side of the gears, are provided, configured to be installed inside the housing between the bearings and the gears. The vertical plates comprise one or more shields, which may be referred to as "external shields", mounted on the side of the vertical plates oriented towards the exterior of the housing, each external plate being formed in a "U-shape" configured to surround one of the bearings. In particular, the system comprises one or more shields, which may be referred to as "internal shields", mounted on the side of the vertical plates oriented towards the gears, and in particular, at least one anti-recirculation plate includes one or more vertical fins to impede the axial flow of the air-oil mixture. The system may be further configured as described above or below.

[0022] Further explanation and details of the invention are given on the basis of several embodiments illustrated in the following several figures, in which like reference numerals are used for like and corresponding parts, and in which: [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram of a gearbox according to the present invention, shown in cross section. [Diagram 2] FIG. 2 is an enlarged view of the outer shield of FIG. [Diagram 3] FIG. 3 illustrates an embodiment of an anti-recirculation plate according to the present invention. [Figure 4] FIG. 4 is a schematic diagram of a preferred embodiment of a cooling system according to the present invention. [Diagram 5] FIG. 5 is a more detailed schematic diagram of an anti-recirculation plate according to the present invention. [Figure 6]FIG. 6 is a more detailed schematic diagram of an anti-recirculation plate according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In FIG. 1, a gearbox (or transmission) 1 with a system for reducing TPL according to a preferred embodiment of the invention is illustrated. The gearbox 1 comprises a number of gears, namely a first gear 11 and a second gear 12, as known in the art, whose teeth mesh with one another. This meshing takes place in a meshing area M (see FIG. 4). Due to this meshing, a rotation of the first gear 11 according to a rotation direction w1 (see the corresponding arrow in FIG. 4) causes the second gear to rotate according to a rotation direction w2 (see the corresponding arrow in FIG. 4), and vice versa. Each gear is fixed to a rotating shaft supported by at least one bearing (or bearings) mounted in the gearbox housing 10. The rotating shaft is then allowed to rotate around its central axis of rotation. For example, a first gear 11 is mounted on a first rotating shaft 13 supported by at least one bearing 15, and a second gear 12 is mounted on a second rotating shaft 14 supported by at least one bearing 16. Typically, both bearings 15, 16 are supported in the housing 10. Preferably, two bearings support the rotating shafts 13, 14, one on each side of the gear to which the rotating shafts are attached.

[0025] The system for reducing the TPL is provided with one or more vertical plates 2. At least one vertical plate 2 is provided for each bearing of the gearbox to separate said bearing 15, 16 from the gears 11, 12. As mentioned above, "vertical" means a direction substantially perpendicular to the axis of rotation. The vertical plates are simple side panels (or side plates) attached to each side of the gears 11, 12, between the bearings 15, 16 supporting the axis of rotation 13, 14 and the gears 11, 12. To this end, each vertical plate 2 is a thin plate, preferably a metal plate, with two sides, one of which is oriented towards the gears 11, 12, i.e. facing the gears 11, 12, and the other of which is oriented towards the outside of the housing 10, i.e. facing the wall of the housing.

[0026] As illustrated in FIG. 1, the vertical plate 2 is placed in the axial space separating the gears 11, 12 from the bearings 15, 16. The same is true for the other side of the gears 11, 12, i.e. another vertical plate 2 is placed. Each vertical plate is preferably perpendicular to the central axis of rotation of the rotating shafts 13, 14. However, other configurations can be envisaged depending on the geometry of the housing, the bearings and the gears. Thus, in the present invention, for the gears 11, 12 mounted on the rotating shafts 13, 14 supported on both sides of the gears by the bearings 15, 16, two vertical plates 2 can be placed in the housing 10, one vertical plate on one side of the gears and the other vertical plate on the other side of the gears. Thus, as illustrated in FIG. 1, the gears are sandwiched between the vertical plates.

[0027] The vertical plate 2 according to the present invention is constructed as follows. i.e., configured to separate a first oil flow provided for cooling and / or lubricating the gears from a second oil flow provided for cooling and / or lubricating the bearings; and / or The first oil flow is configured to separate (or isolate) the oil flow intended to cool the gears (which is directed towards the blowing surface located behind the meshing area with respect to the rotation of the gears) from the oil flow intended primarily to lubricate the gears (which is therefore directed towards the meshing area).

[0028] For said separation of the different oil flows, the vertical plate according to the invention comprises a shielding system consisting of one or more shields, which separate the different oil flows in the gearbox housing. In particular, said shield or shields act like fenders or hoods, preferably metallic shields, which are arranged to be attached to the vertical plate. Each vertical plate 2 is preferably a removable plate, allowing it to be easily removed from the housing 10 and easily installed inside it. Each vertical plate 2 preferably consists of two separate plates, namely an upper plate 21 and a lower plate 22, mounted one above the other, for example vertically aligned one above the other, to form said vertical plate 2. Each vertical plate 2 is provided with at least two openings, each of which is fitted to one of said rotation shafts 13, 14, and which are therefore provided as circular openings. Preferably, each opening is provided in both the upper and lower plates, i.e. has one edge in the form of a circular arc that is part of the upper plate and the other edge in the form of a circular arc that is part of the lower plate, so that when the upper and lower plates are assembled, these two edges together form said circular opening so as to fit the diameter of the corresponding rotating shaft. The distribution of the two edges of each opening in the lower and upper plates allows easy mounting of the vertical plates in the housing of the gearbox.

[0029] The shielding (or covering) system according to the invention comprises at least an outer shield and / or an inner shield. The outer shield is configured to separate a first oil flow from a second oil flow. It is called "outer" because it is attached to the side of the vertical plate 2 oriented towards the bearing (i.e. its surface normal is towards the bearing). The inner shield is configured to separate the cooling oil flow from the lubricating oil flow for said first oil flow. It is called "inner" because it is attached to the side of the vertical plate 2 oriented towards the gears, i.e. towards the inside of the housing.

[0030] The outer shield is configured to at least partially surround the bearings 15, 16. In the present invention, each bearing 15, 16 may be partially surrounded by an outer shield. Each outer shield is preferably characterized by an inverted U-shape, which opens towards the bottom of the housing so that the oil flows by gravity towards said bottom. In particular, the outer shield comprises a first part 210 consisting of a curved part, e.g. a curved plate, and optionally a second part 220 consisting of a flat straight part, e.g. a flat straight plate, said first part 210 and said second part 220 together forming said inverted U-shape. Preferably, the first part 210 is attached to the upper plate 21 and the second part 220 (if provided) is attached to the lower plate 22. The first part 210 is configured to surround the upper part of the bearing 15, 16 in order to collect the centrifuged oil of the bearing. The second part 220 is configured to extend the tip of the upper part 210 towards the bottom of the housing 10, thereby guiding the collected oil towards a receptacle or oil pan of the housing 10 or an oil tank, so that the collected oil flows from the top to the bottom (or bottom) by gravity during the operation of the gearbox. The first part 210 can have a semicircular shape to follow the circumference of the bearings 15, 16 and can be spaced apart from the bearings 15, 16. The first part 210 acts like a hood configured to collect the oil splashed by the bearings 15, 16, forcing the oil to remain within the volume enclosed by the outer shield. The upper plate 21 is vertically installed on the lower plate 22, and the end of the first part 210 of the outer shield is fitted between the multiple secondary plates of the second part 220 to preferably form the inverted "U" shape for each bearing 15, 16. The first portion 210 corresponds to the curved portion of the inverted U-shape, and the second portion 220 constitutes each bar (or straight portion) of the inverted U-shape. Preferably, the curved portion fits between the bars of the U-shape, i.e., slots the space separating the bars of the U-shape.Due to this geometrical shape of each outer shield, the oil splashed by the bearings is collected inside the U-shape and guided along the U-shaped bar towards a receptacle, for example towards a receptacle arranged below the bearings 15, 16. A closer look at the outer shield is illustrated in Figure 2. On the side of the vertical plate including said outer shield, the vertical plate further comprises one or more chocks (or wedges) 223.

[0031] In Fig. 3 the interior of the housing 10 of the gearbox according to the invention is illustrated. As mentioned above, the vertical plate 2 can also be equipped with an internal shield to separate the different oil flows. Said internal shield comprises anti-recirculation plates 230, 240 which can be fixed to the vertical plate 2 and in particular to one or both of the lower plates and / or one or both of the upper plates 21, 22 which sandwich the gears 11, 12. The anti-recirculation plates 230, 240 are arranged to separate the oil flow of a cooling system 30 arranged to cool the angular section of the gears 11, 12 from another oil flow originating from said cooling system 30, which not only has a cooling function but also a function of lubricating the meshing area M. This system is therefore a cooling and lubrication system or a lubrication system, said other oil flow being essentially arranged to lubricate the meshing area M of the gears 11, 12.

[0032] The cooling system 30 according to the invention comprises in particular one or more cooling nozzles 31A, 31B, where a first set of cooling nozzles 31A of the cooling system 30 is adapted to spray the outer surface of the first gear 11 and a second set of cooling nozzles 31B of the cooling system 30 is adapted to spray the outer surface of the second gear 12. Said outer surface defines for the gear a single angular section extending along the entire width (i.e. axial direction) of the gear, the arc of which is sprayed by one of the cooling nozzles. Each set of the cooling nozzles 31A, 31B is thus adapted to spray a defined area on the outer surface of the gear, which area is located behind the meshing area M, for example substantially below the meshing area M. Preferably, each nozzle jet makes an angle with the outer surface of the gear included in the range [90°, 180°], with a value of 90° being preferred, as illustrated in figures 3 and 4.

[0033] In addition to the cooling nozzles 31A, 31B, the system according to the invention comprises one or more lubrication nozzles 32, which may be part of the cooling system 30 shown in the embodiment of figures 3 and 4, or of a separate, independent lubrication system (not shown). The oil flow dispersed by said lubrication nozzles 32 is preferably controlled by a feedback loop which is a function of the temperature in the housing 10. In particular, this oil flow is oriented parallel to the tangential velocity vector defined on the outer surface of the gears. The oil flow is preferably sprayed at the top of the meshing area M. For example, the oil flow has a substantially vertical direction and is directed to the bottom, so that both the first and second gears are lubricated simultaneously. Alternatively, the oil flow may be sprayed only on the gear 14 with the lowest rotational speed, in the area immediately before and adjacent to said meshing area (M). Preferably, the lubrication nozzles 32 are connected with a secondary duct 34 which supplies them with oil. This secondary duct 34 is connected to a main duct 33 arranged to supply the cooling nozzles 31A, 31B with oil. Preferably, the secondary duct 34 passes through a recirculation prevention plate 230 which comprises openings 234 (see Figures 1, 5 or 6) fitted over the entire or at least part of the circumference of the secondary duct 34, thereby preventing the mixture of air and oil resulting from the oil sprayed by the cooling nozzles from passing through said openings and reaching the volume located above the recirculation prevention plate 230.

[0034] Preferably, as illustrated in Figures 5 and 6, the recirculation prevention plate 230 comprises a U-shaped plate 235, for example bent into a U-shape and preferably welded to the recirculation prevention plate 230, in a configuration surrounding the secondary duct 34 with a U-shaped curve, with the U-shaped arm extending towards the wall 17 of the housing 10, i.e. towards the second edge 230B of the recirculation prevention plate 230. The U-shaped plate 235 forms the opening 234 in the recirculation prevention plate 230, so as to fit into the secondary duct 34. In fact, the curved part of the U-shape forms a surface that substantially vertically surrounds a given length of the secondary duct. In particular, a normal to the surface, substantially parallel to the arm of the U-shape, is directed towards the cooling system 30. Thus, the curved portion of the U-shape is configured to prevent the flow of the mixture of air and oil, which flows from the cooling system 30 towards the wall 17. In this regard, the space managed between the arms of the U-shape allows the recirculation prevention plate 230 to be easily aligned. The U-shaped plate 235 is preferably perpendicular to the first inclined surface 231 and the second inclined surface 232 of the recirculation prevention plate 230. In particular, the arms of the U-shape each form a substantially vertical surface connected with the curved surface of the U-shape and are parallel to the vertical fins 233 of the recirculation prevention plate 230.

[0035] In the embodiment illustrated in Figures 3 and 4, the internal shield according to the invention preferably comprises two anti-recirculation plates for separating the cooling oil flow from the lubricating oil flow of the gears 11, 12. The first anti-recirculation plate 230 cooperates with the first gear 11, i.e. with the gear characterized by the highest rotational speed, and the second anti-recirculation plate 240 cooperates with the second gear 12, i.e. with the gear characterized by the lowest rotational speed, to separate the oil flows as described above. Hereinafter, the term "anti-recirculation plate" will be used to describe features included in both the first and second anti-recirculation plates, unless otherwise specified.

[0036] The first anti-recirculation plate 230 comprises a first edge 230A oriented towards the outer surface of the first gear 11, characterized by a length at least equal to the width of the first gear and spaced from the outer surface of the first gear by an adjustable distance (typically measured radially). The first anti-recirculation plate 230 comprises a second edge 230B, which is located on the opposite side of the first anti-recirculation plate with respect to the first edge 230A. It is oriented towards (i.e. at a height from) the wall of the housing and a position below the first edge 230A. Thus, oil collected by the anti-recirculation plate in the immediate vicinity of the first edge 230A is allowed to flow by gravity towards the second edge 230B. The second edge 230B is attached to the wall of the housing but is preferably not in contact with the wall of the housing. As a result, the oil flowing on the recirculation prevention plate can freely flow toward the bottom of the housing. Preferably, the first recirculation prevention plate 230A comprises the first inclined surface 231 including the first edge 230A and the second inclined surface 232 including the second edge 230B. In this case, the inclination of the first inclined surface 231 with respect to the horizontal plane is smaller than the inclination of the second inclined surface, and preferably, the inclined surfaces 231, 232 are parallel to the central axis of rotation of the rotating shaft, joined to each other, for example joined to each other by a curved surface, and extend along the width of the first gear 11. Optionally, the first recirculation prevention plate 230 further comprises a vertical fin 233, which is mounted perpendicular to both the first and second inclined surfaces and configured to guide the air-oil mixture, while preventing or obstructing the axial flow caused by the rotation of the gears. Advantageously, said fins further increase the stiffness of the recirculation prevention plate 230. Preferably, the first recirculation prevention plate 230 comprises said opening 234 which is fitted with the secondary duct 34, thereby making it possible to extend said secondary duct 34 from a first volume of the gearbox, located at the bottom of the housing and comprising the cooling nozzles 31A, 31B, to a second volume of the gearbox, located at the top of the housing and comprising the lubrication nozzles 32.Preferably, said opening 234 comprises a U-shaped plate 235 fixed to the recirculation prevention plate and extends substantially vertically along its length, i.e. perpendicular to the recirculation prevention plate 230, above and below the recirculation prevention plate 230, thereby preventing the flow of the air and oil mixture coming from the cooling system 30 (see Figures 5 and 6).

[0037] As illustrated in FIG. 5, the second recirculation prevention plate 240 has a first edge 240A oriented toward the outer surface of the second gear 12, characterized by having a length at least equal to the width of the second gear 12, and spaced from the outer surface of the second gear by an adjustable distance (typically measured radially). The second recirculation prevention plate 240 has a second edge 240B arranged on the opposite side of the second recirculation prevention plate with respect to the first edge 240A, and is therefore oriented toward the wall of the housing and arranged at a position (i.e., at a height) below the first edge 240A. Thus, oil collected by the recirculation prevention plate in the close vicinity of the first edge 240A can flow toward the second edge 240B by gravity. The second edge 240B is attached to the wall of the housing, but preferably does not contact the wall. Therefore, the oil flowing on the recirculation prevention plate can freely flow toward the bottom of the housing. The second recirculation prevention plate 240A preferably includes a first inclined surface 241 including a first edge 240A and a second inclined surface 242 including a second edge 240B. In this case, the inclination of the first inclined surface 241 with respect to the horizontal plane is smaller than the inclination of the second inclined surface, and preferably, the inclined surfaces 241 and 242 are parallel to the central axis of rotation of the rotating shaft, joined to each other, for example, joined by a curved surface, and extend along the width of the first gear 11.

[0038] The adjustable distance to the outer surface of both the first and second anti-recirculation plates allows to minimize the space between the first edge 230A, 240A and the outer surface of the gears, so that the first edge 230A, 240A remains out of contact with the outer surface during operation of the gearbox. This minimization of the space ensures that no additional heating occurs in the housing. To adjust the adjustable distance, the anti-recirculation plates 230, 240 are preferably slidably fixed to the vertical plate 2. The distance between the outer surface and the first edge can typically vary within the range of 2 mm to 7 mm. Higher values ​​of the distance have been shown to reduce the efficiency of the anti-recirculation plates to separate the oil flow in the housing, and higher values ​​have been shown to increase the temperature in the housing 10.

[0039] Preferably, the axial length of the first anti-recirculation plate and / or the second anti-recirculation plate is greater than the width (i.e., axial length) of the gear closest to the supposed anti-recirculation plate. This allows the axial space between the side of the gear and the vertical plate adjacent to said side to be managed. Preferably, each vertical plate 2 comprises, for each anti-recirculation plate 230, 240, a shelf bracket or shelf bracket fixed thereto, configured to slidably support the anti-recirculation plate 230, 240. Furthermore, the cooperation of said shelf bracket and the anti-recirculation plate allows the space between the anti-recirculation plate 230 and the vertical plate 2 to approach an extension length equal to at least 2 / 3 of the distance separating the first edge 230A from the second edge 230B. For example, said shelf bracket extends in the longitudinal direction according to said extension length.

[0040] For both the first and the second anti-recirculation plate, the first inclined surface 231, 241 is characterized in that its extension E towards the tooth of the nearest gear 11 intersects said gear at the base of one of said teeth, for example at the root diameter of the tooth, with the tooth considered being preferably not aligned with the vertical direction V. Preferably, its extension is tangent to the root circle R of the nearest gear and inclines towards the bottom of the housing when moving away from said nearest gear. Preferably, the inclination of the first inclined surface to the horizontal plane is comprised in the range of 0.55° to 25°, i.e. its angle α is comprised in the range [0.55°, 25°].

[0041] According to the invention, the internal shield makes it possible to delimit two separate volumes or regions around the gears 11, 12 inside the housing 10, i.e. an upper volume and a lower volume separated from each other by the internal shield, the meshing gears, the wall of the housing and the vertical plate 2. In the lower volume containing the cooling nozzles 31A, 31B, the oil and air mixture swept away during the rotation of the gears 11, 12 is prevented from connecting with the upper volume by the internal shield, in particular by the above-mentioned anti-recirculation plate. The internal shield together with the vertical plate therefore makes it possible to limit the amount of oil and air mixture occurring in the lower volume that can reach the upper volume.

[0042] Due to the above configuration, the TPL is reduced. In fact, the internal shield reduces the oil recirculation, so that the energy loss due to pumping is reduced as well as the ventilation. As a result, the amount of oil flow required to cool the gears is also reduced. In addition, to reduce the lubricating oil flow that causes losses of pumping power on the teeth, the oil flow sprayed by the lubrication nozzles can be controlled to minimize the flow of lubricating oil required to create an oil film before entering the meshing area M.

[0043] As an advantage, the solution proposed by the invention allows easy access to the gears and therefore facilitates maintenance work, in addition, the gears are not completely enclosed by a plate (the volume inside the housing is simply separated into two areas / volumes), making an additional cooling system unnecessary.

Claims

1. A system for reducing power losses on teeth in a gearbox (1), comprising: at least two meshing gears (11, 12) mounted within a housing (10) and attached to rotating shafts (13, 14) supported by bearings (15, 16), respectively; two vertical plates (2) adapted to be installed in the housing (10), one on each side of the gears (11, 12), between the bearings (15, 16) and the gears (11, 12); Including, The vertical plate (2) comprises one or more shields configured to separate multiple oil flows within the housing (10); said one or more shields (hereinafter referred to as internal shields) are attached to the side of the vertical plate (2) oriented towards said gears (11, 12); The inner shield comprises recirculation prevention plates (230, 240); At least one of the recirculation prevention plates (230, 240) comprises one or more vertical fins (233) adapted to impede the axial flow of the air and oil mixture.

2. The system according to claim 1, wherein the vertical plates (2) each comprise an upper plate (21) and a lower plate (22).

3. The system according to claim 1 or 2, wherein the recirculation prevention plate (230, 240) is slidably mounted relative to the vertical plate (2).

4. 4. The system according to claim 1, wherein the recirculation prevention plates (230, 240) are inclined with respect to a horizontal plane to allow collected oil to flow from a position close to the gears (11, 12) towards a wall of the housing (10).

5. 5. The system according to claim 1, wherein the anti-recirculation plate (230, 240) comprises a first inclined surface (231, 241) whose extension (E) towards the tooth of the nearest gear (11) intersects the gear (11, 12) at a root diameter of one of its teeth and is tangent to the root diameter.

6. 6. The system according to claim 1, wherein the vertical plate (2) is provided with one or more shields (hereinafter referred to as external shields) attached to the side of the vertical plate (2) oriented towards the outside of the housing (10).

7. 7. The system of claim 6, wherein each of the outer shields is formed in an inverted U-shape to surround one of the bearings (15, 16).

8. 8. The system of claim 7, wherein the outer shield comprises a first portion (210) and a second portion (220) formed into a curved plate and a flat plate, respectively, that together form the inverted U-shape around the bearings (15, 16).

9. The system of claim 8, wherein the first portion (210) is attached to an upper plate (21) and the second portion (220) is attached to a lower plate (22).

10. 10. The system of claim 1, further comprising a cooling system (30) including one or more cooling nozzles (31A, 31B) positioned below the gears (11, 12) and configured to direct a cooling oil flow towards an outer surface of the gears (11, 12).

11. at least one cooling nozzle (31A) directing a first cooling oil flow towards the first gear (11); 11. The system of claim 10, further comprising: at least one cooling nozzle (31B) directing a second cooling oil flow toward the second gear (12).

12. 12. The system according to claim 10 or 11, wherein the angle defined by the direction of the cooling oil jet at the outlet side of the cooling nozzles (31A, 31B) and the outer surface of the gear (11, 12) cooled by the cooling oil jet is included in the range of 90° to 180°.

13. at least two meshing gears (11, 12) mounted in a housing (10) and mounted on rotating shafts (13, 14) supported by bearings (15, 16), respectively; and a system according to any one of claims 1 to 12, Including the gearbox.

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