Gear-based transmission assembly with epicyclic gear train with thermal efficiency

Abstract

A gear-based transmission assembly (1) with epicyclic gear train with thermal efficiency, comprising a box-like body (2) for containing at least one epicyclic stage (3) comprising a sun gear (4) which rotates about a main axis (A), at least two planet gears (5) which are mated with the sun gear (4) and are supported in rotation about the main axis (A) and about respective axes (R) which are parallel to the main axis by a planet carrier (6) and an internally toothed ring gear (7) which is mated with the at least two planet gears (5) and is associated integrally with the box-like body (2) and at least one stage (8) for reducing the rotation rate in input to the at least one epicyclic stage (3) mated with the sun gear (4); the at least one reduction stage (8) comprises a driving pinion (9) which rotates about a primary axis (A1) which substantially coincides with the main axis (A), at least two first gears (10) which rotate about respective secondary axes (A2) which are substantially parallel to the primary axis (A1) and are mated with the driving pinion (9), at least two second gears (11), each integral in rotation about a respective secondary axis (A2) with a corresponding first gear (10) and a transmission pinion (12) which rotates about the main axis (A) and meshes with the at least two second gears (11) for transmitting the rotation about the main axis (A) to the sun gear (4).

Description

[0001] GEAR-BASED TRANSMISSION ASSEMBLY WITH EPICYCLIC GEAR TRAIN WITH THERMAL EFFICIENCY

[0002] The present invention relates to a gear-based transmission assembly with epicyclic gear train with thermal efficiency.

[0003] Transmission assemblies with epicyclic gear train are known which substantially comprise a box-like body which internally accommodates a sun gear which rotates about a main axis, two or more planet gears mated on the peripheral region of the sun gear and supported in rotation by a planet carrier which rotates about the main axis, and an internally toothed ring gear which is integral with the box-like body and with which the planet gears are mated. The sun gear constitutes the driving element of the epicyclic gear train and is connected to the motion input axis, while the planet carrier constitutes the transmission element of the gear train itself and is connected to the motion output axis, which is generally coaxial to the main axis.

[0004] An oil bath is provided inside the box-like body to lubricate the moving elements.

[0005] One of the typical problems of these transmission assemblies is the rise in temperature of the oil bath due to the sloshing caused by the moving elements, in particular by the rotation of the planet carrier.

[0006] The rise of the temperature of the oil bath reduces its lubrication capacity, penalizing the maximum power applicable to the transmission assembly.

[0007] To obviate this drawback, it is known to provide a stage for reducing the rotation rate in input to the epicyclic gear train, so as to reduce the rotation rate of the elements of said gear train and, consequently, the stirring of the oil bath.

[0008] In one conventional possible embodiment, the reduction stage comprises a conical pinion which rotates about a motion input axis which is perpendicular to the main axis of the epicyclic gear train and meshes with a bevel gear. In a first case, the bevel gear is integral in rotation about the main axis with the sun gear of the epicyclic gear train. In a second case, the bevel gear rotates about an axis which is parallel to the main axis and there is at least one additional gear set with cylindrical gears which is interposed between the axis of the bevel gear and the main axis of the sun gear.

[0009] This embodiment, while improving the thermal efficiency of the transmission assembly, increases its space occupation and is applicable only in the configurations for use in which a motion input axis perpendicular to the main axis of the epicyclic gear train is provided.

[0010] As an alternative, a further embodiment of a reduction stage is known which is constituted by a gear set comprising a cylindrical driving gear, which rotates about a motion input axis which is parallel to the main axis of the epicyclic gear train, and a cylindrical transmission gear, which is integral in rotation about the main axis with respect to the sun gear, which are mutually mated.

[0011] In this configuration, the motion input axis is parallel and offset with respect to the main axis of the epicyclic gear train.

[0012] This embodiment, too, while improving the thermal efficiency of the transmission assembly, increases its radial space occupation, limiting its possibilities of use, and is applicable only in the configurations for use in which there is a motion input axis which is parallel and offset with respect to the main axis of the epicyclic gear train.

[0013] The aim of the present invention is to eliminate the above-cited drawbacks of the background art, devising a gear-based transmission assembly with epicyclic gear train with thermal efficiency that allows to contain the rise in lubricating oil temperature and has a compact outline and small overall dimensions, especially in the radial direction, so as not to limit its possibilities of use and not to complicate its installation.

[0014] Within this aim, an object of the present invention is to be flexible in use by being able to adapt to configurations for use in which the motion input axis is perpendicular or parallel to the main axis of the epicyclic gear train.

[0015] A further object of the invention is to allow a configuration for use in which the motion input axis is coaxial with the main axis of the epicyclic gear train.

[0016] Not least object of the present invention is to have a simple structure that is relatively easy to provide in practice, safe in use, effective in operation, and relatively low in cost.

[0017] This aim and these and other objects that will become more apparent hereinafter are all achieved by the present gear-based transmission assembly with epicyclic gear train with thermal efficiency according to the principal and independent claim 1, which follows, and optionally provided with one or more of the characteristics set forth in the subsequent dependent claims.

[0018] Further characteristics and advantages of the present invention will become better apparent from the detailed description of a preferred but not exclusive embodiment of a gear-based transmission assembly with epicyclic gear train with thermal efficiency, illustrated by way of non-limiting example in the accompanying drawings, wherein:

[0019] Figure 1 is an axonometric view of a gear-based transmission assembly with epicyclic gear train with thermal efficiency, according to the invention;

[0020] Figure 2 is a sectional view, taken along a plane that passes through the main axis of the transmission assembly of Figure 1;

[0021] Figure 3 is a perspective view of the reduction stage of the transmission assembly according to the invention;

[0022] Figure 4 is a front elevation view of the reduction stage of Figure 3;

[0023] Figure 5 is a sectional view, taken along the plane V-V of Figure 4;

[0024] Figure 6 is a lateral elevation view of the reduction stage of Figure 3;

[0025] Figure 7 is a sectional view, taken along the plane VII- VII of Figure

[0026] 6;

[0027] Figure 8 is a sectional view, taken along the plane VIII- VIII of Figure 6;

[0028] Figure 9 is a schematic view of some alternative configurations for use of the transmission assembly according to the invention;

[0029] Figures 10 and 11 are respective charts showing the variation of the oil bath temperature within two transmission assemblies comprising the same epicyclic gear train paired with a conventional reduction stage or with the reduction stage according to the invention as the input rotation rate changes, the two charts referencing respective ways of connecting the transmission assemblies to the driving motor.

[0030] With reference to the figures, a gear-based transmission assembly with epicyclic gear train with thermal efficiency has been generally designated by the reference numeral 1.

[0031] The transmission assembly 1 comprises a box-like body 2 which internally accommodates:

[0032] - at least one epicyclic stage 3 comprising a sun gear 4 which rotates about a main axis A, at least two planet gears 5 mated along the peripheral region of the sun gear 4 and supported in rotation about the main axis A and respective axes R which are substantially parallel to the main axis by means of a planet carrier 6 and an internally toothed ring gear 7 mated with the at least two planet gears 5 and associated integrally with the box-like body 2, and

[0033] - at least one stage 8 for reducing the rotation rate in input to the at least one epicyclic stage 3 mated with the associated sun gear 4.

[0034] In a variation that is not shown, it is not excluded that two or more epicyclic stages 3 arranged in series may be provided; in this case, the epicyclic stage 3 referred to in the present description is the first in the series along the direction of motion transmission.

[0035] Moreover, in a variation that is not shown, it is not excluded that there may be two or more reduction stages 8 arranged in series; in this case, the reduction stage 8 to which the present description refers is the last in the series along the direction of motion transmission.

[0036] In the present description, the term "substantially" means “apart from usual machining and assembly tolerances of the component parts”.

[0037] The axes of rotation R of the planet gears 5 are arranged on a circumference centered on the main axis A of the sun gear 4. The planet gears 5 are arranged symmetrically around the sun gear 4. Preferably, there are at least three planet gears 5. In the embodiment shown there are four planet gears 5 (only two of which are visible in Figure 2), distributed around the sun gear 4 in pairs, 90° apart.

[0038] The planet carrier 6 has a substantially annular extension around the main axis A and has a connecting flange for transmitting rotation to the output axis or other transmission element connected downstream of the epicyclic stage 3 along the direction of motion transmission.

[0039] The ring gear 7 has an annular shape centered on the main axis A.

[0040] In the embodiment shown, an epicyclic stage 3 and a reduction stage 8 are provided which are mutually mated, the reduction stage 8 being adapted to transfer the rotation to the sun gear 4 of the epicyclic stage 3.

[0041] It should be noted that the box-like body 2 can have different geometries and dimensions and can be provided in two or more parts assembled together, depending on the requirements of the specific application.

[0042] According to the invention, the reduction stage 8 comprises:

[0043] - a driving pinion 9, which rotates about a primary axis Al which substantially coincides with the main axis A;

[0044] - at least two first gears 10, which rotate about respective secondary axes A2 which are substantially parallel to the primary axis Al and are mated with the driving pinion 9. The first gears 10 are distributed around the peripheral region of the driving pinion 9. The secondary axes A2 are positioned on a circumference centered on the primary axis Al;

[0045] - at least two second gears 11, each integral in rotation about a respective secondary axis A2 wet a corresponding first gear 10; and

[0046] - a transmission pinion 12, which rotates about the main axis A and is engaged with the at least two second gears 11 for transmitting rotation about the main axis A to the sun gear 4 in input to the epicyclic stage 3. The second gears 11 are distributed around the peripheral region of the transmission pinion 12.

[0047] Preferably, the at least two secondary axes A2 with the corresponding first and second gears 10 and 11 are distributed substantially symmetrically around the primary axis Al and the main axis A, respectively. This balances the stresses on the axes and rotating elements.

[0048] Even more preferably, the reduction stage 8 provides for three first gears 10 which rotate about respective secondary axes A2 and three corresponding second gears 11, each meshed with one of the first gears 10.

[0049] In the preferred embodiment, the three secondary axes A2 with the corresponding first and second gears 10 and 11 are symmetrically distributed around the primary axis Al and the main axis A in pairs, spaced by an angle substantially equal to 120° (Figures 7 and 8).

[0050] In an alternative embodiment, not shown, the reduction stage 8 may comprise, for example, four first gears 10 rotating about respective secondary axes A2 and four corresponding second gears 11 , each meshing with one of the first gears 10. Preferably, the four secondary axes A2 with the corresponding first and second gears 10 and 11 are symmetrically distributed around the primary axis Al and the main axis A.

[0051] Preferably, the driving pinion 9, the first gears 10, the second gears 11 and the transmission pinion 12 are of the straight-tooth type.

[0052] The reduction stage 8 comprises a shaft 13 for supporting the driving pinion 9 lying along the primary axis Al. By virtue of the particular configuration assumed by the first gears 10, the shaft 13 and the driving pinion 9 are supported in rotation about the primary axis Al directly by the first gears, without the need for bearings or the like interposed between the shaft 13 and the box-like body 2. The driving pinion 9 is mounted floating between the first gears 10 inside the box-like body 2.

[0053] In a variation, the driving pinion 9 and the shaft 13 might be provided integrally monolithically.

[0054] The transmission pinion 12 is also supported in rotation by the second gears 11 without requiring bearings or the like. The transmission pinion 12 is mounted floating between the second gears 11 inside the box-like body 2.

[0055] Moreover, in the embodiment shown, the transmission pinion 12 in output from the reduction stage 8 is directly mated with the sun gear 4 of the epicyclic stage 3. In particular, there is a prismatic connection with splined profiles between the transmission pinion 12 and the sun gear 4, but different types of mechanical connection are not excluded.

[0056] In this way, the transmission pinion 12 supports the sun gear 4 in rotation about the main axis A.

[0057] It is not excluded that other elements may be interposed between the transmission pinion 12 and the sun gear 4 to transmit the rotation so as to obtain an indirect connection.

[0058] Advantageously, each first gear 10 and the corresponding second gear 11 are associated so as to be integral in rotation with a pivot 14 which lies along the respective secondary axis A2. Each pivot 14 is rotationally supported about its respective secondary axis A2 within the box-like body 2.

[0059] In this way, each first gear 10, the corresponding second gear 11, and the corresponding pivot 14 form a pre-assembled subassembly, which can be easily placed in its seat during the assembly of the assembly 1 or removed from its seat for possible maintenance.

[0060] Advantageously, it is possible to provide a single element 15 for connection by interposed obstacle, of the type of a key or the like, interposed between each of the first gear 10, the corresponding second gear 12, and the respective pivot 14. The slot for accommodating the keyway 15 is formed on each first gear 10 and the corresponding second gear 11 at such an angle as to achieve in-phase assembly of said gears on the respective pivot 14.

[0061] In this way, the first gear 10 and the corresponding second gear 11 are positioned around the corresponding pivot 14 with their respective teeth axially aligned in the assembly step, without requiring special arrangements, external constraints, or adjustment operations performed in situ to obtain their phasing.

[0062] As an alternative, at least one of the first and second gears 10 or 11 may be provided integrally and monolithically with the corresponding pivot 14.

[0063] Each pivot 14 is rotationally supported within the box-like body 2 by conventional bearings 17 located at the mutually opposite ends.

[0064] Arrows are shown in Figure 5 which indicate the direction of motion transmission through the reduction stage 8, from the shaft 13 with the driving pivot 9, passing through each assembly constituted by first gear 10- pivot 14-second gear 11, up to the transmission pinion 12.

[0065] Figures 1 and 2 show a conventional assembly 16 for connection to rotary actuation means (not shown) directly associated with the shaft 13. In this case, the transmission assembly 1 can be used in applications in which the motion input axis is substantially coaxial with the primary axis Al and the main axis A. However, alternative configurations for use of the transmission assembly 1 are not ruled out.

[0066] For example, Figure 9 shows schematically some possible configurations for use of the transmission assembly 1 according to the invention, comprising an epicyclic stage 3 associated with a reduction stage 8. As an alternative, the following can be provided in input to the reduction stage 8:

[0067] - a conventional bevel gear C constituted by a conical pinion associated with means (not shown) for actuation in rotation about an axis which is perpendicular to the primary axis Al and a bevel gear which rotates about an axis which substantially coincides with the primary axis Al and is integral in rotation with the driving pinion 9 of the reduction stage 8, mutually coupled;

[0068] - an additional epicyclic stage E of the known type, extending along an axis which is substantially coaxial to the primary axis Al and having its planet carrier integral in rotation with the driving pinion 9 of the reduction stage 8;

[0069] - generic rotary drive means M directly connected to the driving pinion 9 of the reduction stage 8, such as for example a conventional electric motor.

[0070] Moreover, it should be noted that a lubricating oil bath is conventionally provided inside the box-like body 2, and therefore the boxlike body 2 is provided with sealing elements which are not shown in detail since they are of a known type.

[0071] In this regard, it has been found that in the transmission assembly 1 according to the invention, the special configuration of the reduction assembly 8 allows to greatly reduce the stirring of the oil bath and the consequent rise in temperature, with considerable improvement in the performance and efficiency of the assembly with respect to reduction assemblies employing other known types of reduction assembly at the input of the epicyclic gear train.

[0072] Each of the charts shown in Figures 10 and 11 plots two curves representing the trend of the temperature measured in the oil bath inside two different transmission assemblies constituted by the same epicyclic gear train associated in input, in one case, with a conventional parallel-axes reduction stage (upper curve labeled "CONVENTIONAL") and, in the other, with the reduction stage 8 according to the invention (lower curve labeled "NEW"). The two charts of Figures 10 and 11 differ in the way the transmission assemblies are connected to the drive motor. In fact, in the transmission assemblies of Figure 10 there is a direct connection to the motor, while in the assemblies of Figure 11 there is a connection by interposing a cylindrical shaft connection, typically used for pulley or cardan coupling.

[0073] Both charts show that as the input rotation rate increases, the oil bath temperature in the transmission assembly 1 according to the invention undergoes a smaller increase than in conventional assemblies. Moreover, it can be noted that as the input rotation rate increases, in the transmission assembly 1 according to the invention the oil bath temperature increases with a substantially linear trend, whereas for conventional assemblies the temperature increases much more rapidly. Moreover, it can be noted that conventional assemblies undergo failure for a certain value of input rotation rate (denoted by "break down point") beyond which they cannot work, while the transmission assembly 1 according to the invention continues to operate even for higher input rotation rates.

[0074] In practice it has been found that the described invention achieves the intended aim and objects, and in particular it is emphasized that the transmission assembly according to the invention allows to reduce the rotation rate of the epicyclic stage elements in order to limit the stirring of the lubricating oil bath, increasing overall efficiency by virtue of the presence of a compact reduction stage that does not entail any increase in space occupation in a radial direction of the transmission assembly.

[0075] Moreover, the transmission assembly according to the invention can be used in different configurations for use, with the input axis both parallel and perpendicular to the output axis.

[0076] In particular, the transmission assembly according to the invention can be applied in configurations for use which provide for coaxial input and output axes.

[0077] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

[0078] All the details may furthermore be replaced with other technically equivalent elements.

[0079] In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to the requirements without thereby abandoning the protective scope of the claims that follow.

[0080] The disclosures in Italian Patent Application No. 102023000017580 from which this application claims priority are incorporated herein by reference. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

CLAIMS1. A gear-based transmission assembly (1) with epicyclic gear train with thermal efficiency, comprising a box-like body (2) for containing at least one epicyclic stage (3) comprising a sun gear (4) which rotates about a main axis (A), at least two planet gears (5) which are mated with said sun gear (4) and are supported in rotation about said main axis (A) and about respective axes (R) which are parallel to said main axis by a planet carrier (6) and an internally toothed ring gear (7) which is mated with said at least two planet gears (5) and is associated integrally with said boxlike body (2) and at least one stage (8) for reducing the rotation rate in input to said at least one epicyclic stage (3) mated with said sun gear (4), characterized in that said at least one reduction stage (8) comprises a driving pinion (9) which rotates about a primary axis (Al) which substantially coincides with said main axis (A), at least two first gears (10) which rotate about respective secondary axes (A2) which are substantially parallel to said primary axis (Al) and are mated with said driving pinion (9), at least two second gears (11), each integral in rotation about a respective secondary axis (A2) with a corresponding first gear (10) and a transmission pinion (12) which rotates about said main axis (A) and meshes with said at least two second gears (11) for transmitting the rotation about said main axis (A) to said sun gear (4).

2. The assembly (1) according to claim 1, characterized in that said at least two secondary axes (A2) with the corresponding first and second gears (10, 11) are distributed substantially symmetrically around said primary axis (Al), which substantially coincides with said main axis (A), respectively.

3. The assembly (1) according to claim 1 or 2, characterized in that said reduction assembly (8) comprises three of said first gears (10), which rotate about respective secondary axes (A2) and are mated with three corresponding second gears (11).

4. The assembly (1) according to claims 2 and 3, characterized in that said three secondary axes (A2) with the corresponding first and second gears (10, 11) are distributed around said primary axis (Al) which substantially coincides with said main axis (A) in pairs, which are spaced by an angle substantially equal to 120°.

5. The assembly (1) according to one or more of the preceding claims, characterized in that said reduction assembly (8) comprises a shaft (13) for supporting said driving pinion (9) which lies along said primary axis (1), the shaft (13) and the driving pinion (9) being supported in rotation about said primary axis (Al) by said at least two first gears (10).

6. The assembly (1) according to one or more of the preceding claims, characterized in that said transmission pinion (12) is directly mated with said sun gear (4).

7. The assembly (1) according to one or more of the preceding claims, characterized in that each of said at least two first gears (10) and the corresponding second gear (11) are integrally associated in rotation with a pivot (14) which lies along the respective secondary axis (A2).

8. The assembly (1) according to claim 7, characterized in that it comprises a single element (15) for connection, by interposed obstacle, between each of said at least two first gears (10), the corresponding second gear (11) and the respective pivot (14).

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