Gear-based transmission assembly with a planetary gear train having thermal efficiency

Abstract

A gear-based transmission assembly (1) having a thermally efficient planetary gear train includes a box-shaped body (2), the box-shaped body (2) includes a sun gear (4) that rotates around a main shaft (A), at least two planetary gears (5) that mesh with the sun gear (4) and are supported by planetary carriers (6) in rotation around the main shaft (A) and around each axis (R) parallel to the main shaft, at least one planetary stage (3) that meshes with the at least two planetary gears (5) and has internally toothed ring gears (7) integrally associated with the box-shaped body (2), and at least Each gear is for housing one stage (8), and each reduction stage (8) includes a drive pinion (9) that rotates around a primary shaft (A1) substantially coinciding with the main shaft (A), at least two first gears (10) that rotate around each secondary shaft (A2) substantially parallel to the primary shaft (A1) and mesh with the drive pinion (9), at least two second gears (11) each integral with the corresponding first gear (10) in rotation around each secondary shaft (A2), and a transmission pinion (12) that rotates around the main shaft (A) and meshes with at least two second gears (11) to transmit the rotation around the main shaft (A) to the sun gear (4).

Description

Technical Field

[0001] The present invention relates to a gear-based transmission assembly having an epicyclic gear train with thermal efficiency. Transmission assemblies having an epicyclic gear train are known. Such a transmission assembly substantially includes a housing that houses therein a sun gear that rotates around a main shaft, two or more planet gears that mesh in a peripheral region of the sun gear and are rotationally supported by a planet carrier that rotates around the main shaft, and a ring gear having teeth provided therein that is integral with the housing and with which the planet gears mesh. The sun gear constitutes a driving element of the epicyclic gear train and is connected to a motion input shaft, while the planet carrier constitutes a transmission element of the gear train itself and is connected to a motion output shaft that is generally coaxial with the main shaft.

[0002] An oil bath is provided inside the housing to lubricate the moving elements. One of the typical problems of these transmission assemblies is the temperature rise of the oil bath due to sloshing caused by the rotation of the moving elements, particularly the planet carrier.

[0003] The temperature rise of the oil bath reduces its lubricating ability and disadvantages the maximum output applicable to the transmission assembly.

[0004] To prevent this drawback, it is known to provide a stage for reducing the rotational speed at the input to the epicyclic gear train to reduce the rotational speed of the elements of the gear train, and as a result, reduce the agitation of the oil bath.

[0005] In one conventional possible embodiment, the reduction stage includes a bevel pinion that rotates around a motion input shaft perpendicular to the main shaft of the epicyclic gear train and meshes with a bull gear. In the first case, the bull gear is integral with the sun gear of the epicyclic gear train in rotation around the main shaft. In the second case, the bull gear rotates around an axis parallel to the main shaft, and there is at least one additional gear set having a cylindrical gear that intervenes between the axis of the bull gear and the main shaft of the sun gear.

[0006] This embodiment is applicable only to configurations for use in which the thermal efficiency of the transmission assembly is improved while increasing its spatial occupancy, and a motion input shaft perpendicular to the main axis of the planetary gear train is provided.

[0007] As an alternative, further embodiments of the reduction stage are known, which comprise a gear set including cylindrical drive gears that mesh with each other and rotate around motion input shafts parallel to the main shafts of the planetary gear train, and cylindrical transmission gears that are integral with the sun gear in rotation around the main shaft.

[0008] In this configuration, the motion input axis is parallel to and offset from the principal axis of the planetary gear train.

[0009] This embodiment, while improving the thermal efficiency of the transmission assembly, also increases its radial space occupancy, limiting its range of use, and is only applicable in configurations where a motion input shaft exists that is parallel and offset to the main axis of the planetary gear train.

[0010] The objective of the present invention is to eliminate the aforementioned drawbacks of the background art and to devise a gear-based transmission assembly having a thermally efficient planetary gear train that can suppress the temperature rise of the lubricating oil and has a compact external shape and small overall dimensions, particularly in the radial direction, without limiting the possibilities of use and without complicating its installation.

[0011] Within this objective, an object of the present invention is to be flexible in use by being adaptable to configurations for use in which the motion input axis is perpendicular or parallel to the principal axis of the planetary gear train.

[0012] A further object of the present invention is to enable a configuration for use in which the motion input shaft is coaxial with the main axis of the planetary gear train.

[0013] In particular, an object of the present invention is to have a simple structure that is relatively easy to provide in practice, safe to use, effective in operation, and relatively low-cost.

[0014] All of these objectives and other objectives, which will become more apparent below, are achieved by the gear-based transmission assembly having a thermally efficient planetary gear train as described in the following main independent claim 1, and optionally one or more of the features described in the subsequent dependent claims.

[0015] Further features and advantages of the present invention will become more apparent from a detailed description of preferred but non-exclusive embodiments of gear-based transmission assemblies having a thermally efficient planetary gear train, as shown in the accompanying drawings as non-limiting examples. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is an unequal projection view of a gear-based transmission assembly having a thermally efficient planetary gear train according to the present invention. [Figure 2] Figure 2 is a cross-sectional view along a plane passing through the principal axis of the transmission assembly in Figure 1. [Figure 3] Figure 3 is a perspective view of the reduction stage of the transmission assembly according to the present invention. [Figure 4] Figure 4 is a front view of the reduction stage shown in Figure 3. [Figure 5] Figure 5 is a cross-sectional view along the plane VV in Figure 4. [Figure 6] Figure 6 is a side view of the deceleration stage shown in Figure 3. [Figure 7] Figure 7 is a cross-sectional view along plane VII-VII in Figure 6. [Figure 8] Figure 8 is a cross-sectional view along plane VIII-VIII in Figure 6. [Figure 9] Figure 9 is a schematic diagram of several alternative configurations for the use of the transmission assembly according to the present invention. [Figure 10]FIG. 10 is a respective chart showing the fluctuations in the oil bath temperature within two transmission assemblies each including the same planetary gear train combined with a conventional reduction stage or the reduction stage according to the present invention when the input rotational speed changes, and the chart refers to each mode of connecting the transmission assembly to the drive motor. [Figure 11] FIG. 11 is a respective chart showing the fluctuations in the oil bath temperature within two transmission assemblies each including the same planetary gear train combined with a conventional reduction stage or the reduction stage according to the present invention when the input rotational speed changes, and the chart refers to each mode of connecting the transmission assembly to the drive motor.

DETAILED DESCRIPTION OF THE INVENTION

[0017] Referring to the drawings, a gear-based transmission assembly having a planetary gear train with thermal efficiency is generally designated by reference numeral 1.

[0018] The transmission assembly 1 includes a box-shaped body 2, and the box-shaped body 2 - a sun gear 4 that rotates around the main shaft A, and at least two planetary gears 5 that mesh along the peripheral region of the sun gear 4 and are supported in rotation around the main shaft A by the planetary carrier 6 and around respective axes R substantially parallel to the main shaft, and a ring gear 7 having teeth provided inside and meshing with the at least two planetary gears 5 and integrally associated with the box-shaped body 2, and at least one planetary stage 3 including - at least one reduction stage 8 for reducing the rotational speed at the input to at least one planetary stage 3 that meshes with the associated sun gear 4, and is housed inside.

[0019] In a modification not shown, it is not excluded that two or more planetary stages 3 arranged in series may be provided, and in this case, the planetary stage 3 referred to in this description is the first stage in series along the direction of motion transmission.

[0020] Furthermore, in a modification not shown, the existence of two or more reduction stages 8 arranged in series is not excluded. In this case, the reduction stage 8 referred to in this description is the last stage in series along the direction of motion transmission.

[0021] In this description, the term "substantially" means "excluding the normal machining and assembly tolerances of the components".

[0022] The rotation axis R of the planetary gear 5 is arranged on the outer circumference centered on the main shaft A of the sun gear 4. The planetary gears 5 are arranged symmetrically around the sun gear 4. Preferably, there are at least three planetary gears 5. In the shown embodiment, there are four planetary gears 5 (only two of which are visible in FIG. 2), which are distributed in pairs 90° apart around the sun gear 4.

[0023] The planetary carrier 6 has a substantially annular extension around the main shaft A and has a connection flange for transmitting rotation to an output shaft or other transmission element connected downstream of the planetary stage 3 along the direction of motion transmission.

[0024] The ring gear 7 has an annular shape centered on the main shaft A. In the shown embodiment, a planetary stage 3 and a reduction stage 8 that mesh with each other are provided, and the reduction stage 8 is adapted to transmit rotation to the sun gear 4 of the planetary stage 3.

[0025] Note that the box-shaped body 2 can have different geometric shapes and dimensions according to the requirements of specific applications and can be provided by two or more parts assembled with each other.

[0026] According to the present invention, the reduction stage 8 is - a drive pinion 9 that rotates around a primary axis A1 that substantially coincides with the main shaft A, -Includes at least two first gears 10 that rotate around each secondary axis A2 substantially parallel to the primary axis A1 and mesh with the drive pinion 9, the first gears 10 being distributed around the peripheral region of the drive pinion 9, the secondary axis A2 being positioned on the outer circumference centered on the primary axis A1, and further, - At least two second gears 11, each integral with the corresponding first gear 10 in rotation around its respective secondary axis A2, -Includes a transmission pinion 12 that rotates around the main spindle A and engages with at least two second gears 11 to transmit the rotation around the main spindle A to the sun gear 4 in input to the planetary stage 3, the second gears 11 being distributed around the peripheral region of the transmission pinion 12.

[0027] Preferably, at least two secondary shafts A2 having corresponding first and second gears 10 and 11 are distributed substantially symmetrically around the primary shaft A1 and the main shaft A, respectively. This balances the stresses on the shafts and rotating elements.

[0028] More preferably, the reduction stage 8 provides three first gears 10 that rotate around their respective secondary shafts A2, and three corresponding second gears 11 that mesh with each of the first gears 10.

[0029] In a preferred embodiment, the three secondary shafts A2, each having corresponding first and second gears 10 and 11, are distributed symmetrically in pairs around the primary shaft A1 and the main shaft A, separated by an angle substantially equal to 120° (Figures 7 and 8).

[0030] In alternative embodiments not shown, the reduction gear 8 may include, for example, four first gears 10 rotating around each secondary shaft A2, and four corresponding second gears 11, each meshing with one of the first gears 10. Preferably, the four secondary shafts A2 having corresponding first and second gears 10 and 11 are distributed symmetrically around the primary shaft A1 and the main shaft A.

[0031] Preferably, the drive pinion 9, the first gear 10, the second gear 11, and the transmission pinion 12 are of the straight-tooth type.

[0032] The reduction gear 8 includes a shaft 13 for supporting a drive pinion 9 located along the primary axis A1. Due to a specific configuration assumed by the first gear 10, the shaft 13 and the drive pinion 9 are directly supported by the first gear during rotation around the primary axis A1, without the need for bearings or other interposed between the shaft 13 and the box-shaped body 2. The drive pinion 9 is mounted to float between the first gears 10 within the box-shaped body 2.

[0033] In one modification, the drive pinion 9 and shaft 13 may be provided as a single monolithic unit.

[0034] The transmission pinion 12 is also supported by the second gear 11 during rotation without the need for bearings or the like. The transmission pinion 12 is mounted so as to float between the second gears 11 within the box-shaped body 2.

[0035] Furthermore, in the shown embodiment, the transmission pinion 12 at the output of the reduction stage 8 directly meshes with the sun gear 4 of the planetary stage 3. In particular, there is a prismatic connection with a splined profile between the transmission pinion 12 and the sun gear 4, but other types of mechanical connections are not excluded.

[0036] In this way, the transmission pinion 12 supports the sun gear 4 in rotation around the main shaft A.

[0037] It is not ruled out that other elements may be interposed between the transmission pinion 12 and the sun gear 4 to transmit rotation in order to obtain an indirect connection.

[0038] Advantageously, each first gear 10 and the corresponding second gear 11 are associated with a pivot 14 located along their respective secondary axis A2 so as to rotate together. Each pivot 14 is supported within the box-shaped body 2 so as to be rotatable around its respective secondary axis A2.

[0039] 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 on its seat during the assembly of assembly 1, or removed from its seat for possible maintenance.

[0040] Advantageously, it is possible to provide a single element 15 for connection by an interposed obstacle of the type, such as a key, which is interposed between the first gear 10, the corresponding second gear 12, and each of the pivots 14.

[0041] Slots for accommodating the keyway 15 are formed on each first gear 10 and the corresponding second gear 11 at an angle that achieves in-phase assembly of the gear on each pivot 14.

[0042] In this way, the first gear 10 and the corresponding second gear 11 are positioned around the corresponding pivot 14 in the assembly step with their respective teeth aligned axially, without requiring any special arrangement, external constraints, or in-situ adjustment operations to obtain their phasing.

[0043] Alternatively, at least one of the first and second gears 10 or 11 may be provided integrally and monolithically with the corresponding pivot 14.

[0044] Each pivot 14 is rotatably supported within the box-shaped body 2 by conventional bearings 17 located at opposite ends.

[0045] Figure 5 shows an arrow indicating the direction of motion transmission through the reduction stage 8, from the shaft 13 having the drive pivot 9, through each assembly consisting of the first gear 10, pivot 14, and second gear 11, to the transmission pinion 12.

[0046] Figures 1 and 2 show a conventional assembly 16 for connection to a rotary actuation mechanism (not shown) directly associated with shaft 13. In this case, the transmission assembly 1 may be used in applications where the motion input shaft is substantially coaxial with the primary shaft A1 and the main shaft A. However, alternative configurations for the use of the transmission assembly 1 are not excluded.

[0047] For example, Figure 9 schematically shows several possible configurations for the use of the transmission assembly 1 according to the present invention, including a planetary stage 3 associated with the reduction stage 8. Alternatively, at the input to the reduction stage 8, -A conventional bevel gear C comprising a conical pinion associated with means (not shown) for operation in rotation around an axis perpendicular to the primary axis A1, which are coupled together, and a bevel gear that rotates around an axis substantially coinciding with the primary axis A1 and is integral in rotation with the drive pinion 9 of the reduction stage 8, - An additional planetary stage E of a known type having planetary carriers that extend along an axis substantially coaxial with the primary axis A1 and are integrated with the drive pinion 9 of the reduction stage 8 in rotation, - For example, a conventional rotary drive means M, such as a conventional electric motor, which is directly connected to the drive pinion 9 of the reduction stage 8. It may be provided.

[0048] Furthermore, a lubricating oil bath is conventionally provided within the box-shaped body 2, and therefore, the box-shaped body 2 is provided with a sealing element of a known type, which is not shown in detail.

[0049] In this regard, the transmission assembly 1 according to the present invention, through the special configuration of the reduction assembly 8, makes it possible to significantly reduce the agitation of the oil bath and the resulting temperature rise, and it has been found that the performance and efficiency of the assembly are greatly improved compared to reduction assemblies that employ other known types of reduction assemblies at the input of the planetary gear train.

[0050] The charts shown in Figures 10 and 11 plot two curves representing the temperature trends measured in an oil bath within two different transmission assemblies, each composed of the same planetary gear train, one associated in the input with a conventional parallel-axis reduction stage (the upper curve labeled "Conventional") in one case, and the other with the reduction stage 8 according to the present invention (the lower curve labeled "Novel"). The two charts in Figures 10 and 11 differ in the configuration in which the transmission assembly is connected to the drive motor. In fact, in the transmission assembly in Figure 10, there is a direct connection to the motor, while in the assembly in Figure 11, there is a connection via a cylindrical shaft connection, typically used in pulleys or cardan couplings.

[0051] Both charts show that as the input rotational speed increases, the oil bath temperature in the transmission assembly 1 according to the present invention experiences a smaller increase than that of a conventional assembly. Furthermore, it can be noted that as the input rotational speed increases, the oil bath temperature in the transmission assembly 1 according to the present invention increases with a substantially linear trend, whereas in a conventional assembly the temperature increases much more rapidly. Furthermore, it can be noted that while a conventional assembly experiences failure at a certain input rotational speed value (indicated as a "breakdown point") beyond which it cannot operate, the transmission assembly 1 according to the present invention continues to operate even at higher input rotational speeds.

[0052] In practice, the described invention has been shown to achieve its intended goals and objectives, and in particular, the transmission assembly according to the present invention enables a reduction in the rotational speed of the planetary stage elements to limit the agitation of the lubricating oil bath, and enhances overall efficiency due to the presence of a compact reduction stage without any increase in the radial spatial occupancy of the transmission assembly.

[0053] Furthermore, the transmission assembly according to the present invention can be used in configurations for different uses in which the input shaft is both parallel and perpendicular to the output shaft.

[0054] In particular, the transmission assembly according to the present invention may be applied in a configuration for use that provides coaxial input and output shafts.

[0055] All inventions conceived in this manner can be modified and altered in numerous ways, all within the scope of the attached claims.

[0056] All details can be further replaced with other technically equivalent elements. In practice, the materials used, as well as the associated shapes and dimensions, may be any as required, without thereby waiving the scope of protection of the attached claims.

[0057] The disclosures in Italian Patent Application No. 102023000017580, to which this application claims priority, are incorporated herein by reference.

[0058] Where reference numerals are used to accompany any technical feature mentioned in any claim, these reference numerals are included solely for the purpose of enhancing the understanding of the claim and therefore have no limiting effect on the interpretation of each element exemplified by such reference numerals.

Claims

1. A gear-based transmission assembly (1) having a planetary gear train with thermal efficiency, comprising a box-shaped body (2), The box-shaped body (2) is A sun gear (4) that rotates around a main shaft (A), at least two planetary gears (5) that mesh with the sun gear (4) and are supported by a planetary carrier (6) in rotation around the main shaft (A) and around each axis (R) parallel to the main shaft, and at least one planetary stage (3) including a ring gear (7) which meshes with the at least two planetary gears (5) and has teeth inside, which is integrally associated with the box-shaped body (2), A gear-based transmission assembly (1) for housing at least one stage (8) for reducing the rotational speed in the input to the at least one planetary stage (3) that meshes with the sun gear (4), The transmission assembly (1) is characterized in that the at least one reduction stage (8) includes a drive pinion (9) that rotates around a primary axis (A1) substantially coinciding with the main axis (A), at least two first gears (10) that rotate around each secondary axis (A2) substantially parallel to the primary axis (A1) and mesh with the drive pinion (9), at least two second gears (11), each integral with the corresponding first gear (10) in rotation around the respective secondary axis (A2), and a transmission pinion (12) that rotates around the main axis (A) and meshes with the at least two second gears (11) to transmit rotation around the main axis (A) to the sun gear (4).

2. The assembly (1) according to claim 1, characterized in that the at least two secondary shafts (A2) having corresponding first and second gears (10, 11) are each distributed substantially symmetrically around the primary shaft (A1) which substantially coincides with the main shaft (A).

3. The assembly (1) according to claim 1 or 2, wherein the reduction assembly (8) includes three first gears (10) that rotate around their respective secondary shafts (A2) and mesh with three corresponding second gears (11).

4. The assembly (1) according to claims 2 and 3, characterized in that the three secondary shafts (A2) having corresponding first and second gears (10, 11) are distributed around the primary shaft (A1) in pairs, separated by an angle substantially equal to 120°, substantially coinciding with the main shaft (A).

5. The reduction assembly (8) includes a shaft (13) for supporting the drive pinion (9) located along the primary shaft (1), wherein the shaft (13) and the drive pinion (9) are supported in rotation around the primary shaft (A1) by the at least two first gears (10), characterized in that the assembly (1) according to one or more of the preceding claims.

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

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

8. The assembly (1) according to claim 7, comprising a single element (15) for intervening connection between each of the at least two first gears (10), the corresponding second gear (11), and each of the pivots (14).

Images