WO2019048568A1

WO2019048568A1 - Improved planet carrier.

Info

Publication number: WO2019048568A1
Application number: PCT/EP2018/074051
Authority: WO
Inventors: Roel VERPOORTEN; Wouter TITS; Rudi AERTS
Original assignee: Punch Powertrain NV
Current assignee: Punch Powertrain NV
Priority date: 2017-09-06
Filing date: 2018-09-06
Publication date: 2019-03-14
Anticipated expiration: 2020-03-06
Also published as: DE112018004901T5; CN111247361A; NL2019488B1; CN111247361B

Abstract

L'invention concerne un porte-satellites comprenant une pluralité de ponts planétaires suspendus entre une première paroi porteuse et une deuxième paroi porteuse (22). La deuxième paroi porteuse (22) comporte une pluralité d'interruptions en forme de fente (7A, 7B, 7C) réduisant la rigidité qui correspondent à une pluralité de deuxièmes zones de réception de pont planétaire (32A, 32B, 32C). Chacune des interruptions en forme de fente réduisant la rigidité a une direction de fente longitudinale curviligne ayant une forme en U qui enveloppe un axe de rotation central planétaire (4A, 4B, 4C). Ces interruptions en forme de fente réduisant la rigidité spéciales permettent d'obtenir un équilibrage mutuel amélioré des raideurs des deux parois porteuses. Il en résulte un engrenage amélioré qui s'engrène en charge.The invention relates to a planet carrier comprising a plurality of planetary bridges suspended between a first carrier wall and a second carrier wall (22). The second carrier wall (22) has a plurality of stiffness-reducing slit interruptions (7A, 7B, 7C) that correspond to a plurality of second planetary bridge receiving regions (32A, 32B, 32C). Each of the stiffening-reducing slit interruptions has a U-shaped curvilinear longitudinal slot direction which envelops a planetary central axis of rotation (4A, 4B, 4C). These special stiffness-reducing slit interruptions provide improved mutual balancing of the stiffnesses of the two carrier walls. The result is an improved gear that meshes with the load.

Description

Improved planet carrier.

The invention relates to a planet carrier for a planetary gear set, wherein the planet carrier comprises:

- a main central rotation axis, about which a sun gear and a ring gear for such a planetary gear set are co-axially rotatable when assembled to the planet carrier, wherein an axial direction of the planet carrier is defined as being parallel to said main central rotation axis, and;

- a plurality of planetary central rotation axes, which are parallel to said axial direction, and about which a corresponding plurality of planet gears, respectively, of such a planetary gear set are rotatable when assembled to the planet carrier;

- a first carrying wall and a second carrying wall, which are extending transversely to said axial direction, and which are mutually spaced in said axial direction;

- a plurality of planet axles having said plurality of planetary central rotation axes, respectively, and which are assemblable to, or integrally manufactured with, said corresponding plurality of planet gears, respectively;

and wherein:

- the planet axles are extending in-between the first carrying wall and the second carrying wall, as seen in said axial direction;

- the first carrying wall has a plurality of first planet axle receiving areas where the respective planet axles are suspended from the first carrying wall, and the second carrying wall has a plurality of second planet axle receiving areas where the respective planet axles are suspended from the second carrying wall.

When a planetary gear set having such a planet carrier is used in a drive unit of a vehicle, it transfers the torque in the opposite direction when the vehicle is driving in reverse. Under certain load conditions, said torque causes the abovementioned planetary central rotation axes of the planet axles to substantially misalign relative to the main central rotation axis of the planet carrier. This may lead to substantially deteriorated meshing between the planet axles, on the one hand, and the sun gear and ring gear, on the other hand in such manner that substantially increased NVH (Noise, Vibration and Harshness) and substantially accelerated wear is the end result.

It is an object of the invention to alleviate the abovementioned drawbacks.

For that purpose, the invention provides a planet carrier according to independent claim 1. Preferable embodiments of the invention are provided by dependent claims 2-4.

Hence, the invention provides a planet carrier for a planetary gear set, wherein the planet carrier comprises:

and wherein: - the planet axles are extending in-between the first carrying wall and the second carrying wall, as seen in said axial direction;

- the first carrying wall has a plurality of first planet axle receiving areas where the respective planet axles are suspended from the first carrying wall, and the second carrying wall has a plurality of second planet axle receiving areas where the respective planet axles are suspended from the second carrying wall;

- the first carrying wall has a first stiffness against deformation due to load transmitted by the planet axles at the first planet axle receiving areas in radial directions relative to said planetary central rotation axes, respectively; and

- the second carrying wall has a second stiffness against deformation due to load transmitted by the planet axles at the second planet axle receiving areas in radial directions relative to said planetary central rotation axes, respectively;

characterized in that

the second carrying wall has a plurality of stiffness-reducing slot- shaped interruptions corresponding to said plurality of second planet axle receiving areas, respectively, corresponding to said planetary central rotation axes, respectively, wherein each of said stiffness-reducing slot- shaped interruptions, as seen in axial side view along said axial direction, has a curved longitudinal slot direction having a U-shaped form which envelopes its corresponding planetary central rotation axis, thereby reducing the absolute value of the difference between said first stiffness and said second stiffness as compared to the situation in which said plurality of stiffness-reducing slot- shaped interruptions would have been absent.

In the lastmentioned (hypothetical) situation, in which said plurality of stiffness-reducing slot-shaped interruptions would have been absent, the abovementioned second stiffness of the second carrying wall would be quite substantially higher than the abovementioned first stiffness of the first carrying wall in the sense that this quite substantial difference in stiffness would then result into the abovementioned substantial misalignment of the planetary central rotation axes of the planet axles relative to the main central rotation axis of the planet carrier. This would then lead to the abovementioned substantially deteriorated meshing between the planet axles, on the one hand, and the sun gear and ring gear, on the other hand, which would thus cause substantially increased NVH (Noise, Vibration and Harshness) and substantially accelerated wear, as explained above.

However, thanks to the present invention, which provides the abovementioned special stiffness-reducing slot-shaped interruptions in the second carrying wall, the absolute value of the difference between said first stiffness and said second stiffness is reduced as compared to the situation in which said stiffness-reducing slot-shaped interruptions would have been absent. In other words, thanks to the special stiffness-reducing slot-shaped interruptions according to the invention, the most stiff one of the two carrying walls is weakened to have a stiffness closer to that of the less stiff one, thereby better balancing the stiffnesses of both carrying walls. This results into improved gear meshing, reduced NVH, reduced wear and reduced weight.

In a preferable embodiment of a planet carrier according to the invention, at least one of the first carrying wall and the second carrying wall has at least one lubricant-funnelling shape-discontinuity on a radially inward side of at least one corresponding one, respectively, of the first planet axle receiving areas and the second planet axle receiving areas, said lubricant-funnelling shape-discontinuity being configured for funnelling a lubricant towards at least one corresponding one, respectively, of the planet axles, when said lubricant is adhering to the first carrying wall and/or the second carrying wall concerned while said lubricant is being moved radially outward by centrifugal forces caused by operation of the planet carrier, said terms "radially" and "centrifugal" being defined as being radially and centrifugal relative to the main central rotation axis.

Thanks to the application of such lubricant-funnelling shape- discontinuities in a planet carrier, the amount of centrifugally moved lubricant not reaching the planet axles is reduced, while the amount of centrifugally moved lubricant that actually reaches the planet axles is increased. In addition, the increased flow of lubricant towards the planet axles, as provided by the lubricant-funnelling shape-discontinuities, prevents accumulation of debris near the planet axles, and provides better cooling.

It is noted that, more in general, said at least one lubricant- funnelling shape-discontinuity can be applied in a planet carrier not having the abovementioned stiffness-reducing slot- shaped interruptions, while in that case said at least one lubricant-funnelling shape-discontinuity provides advantages similar to the advantages discussed above. Such a more general planet carrier may be specified as follows.

"A planet carrier for a planetary gear set, wherein the planet carrier comprises:

- a first carrying wall and a second carrying wall, which are extending transversely to said axial direction, and which are mutually spaced in said axial direction; - a plurality of planet axles having said plurality of planetary central rotation axes, respectively, and which are assemblable to, or integrally manufactured with, said corresponding plurality of planet gears, respectively;

and wherein:

characterized in that

at least one of the first carrying wall and the second carrying wall has at least one lubricant-funnelling shape-discontinuity on a radially inward side of at least one corresponding one, respectively, of the first planet axle receiving areas and the second planet axle receiving areas, said lubricant-funnelling shape-discontinuity being configured for funnelling a lubricant towards at least one corresponding one, respectively, of the planet axles, when said lubricant is adhering to the first carrying wall and/or the second carrying wall concerned while said lubricant is being moved radially outward by centrifugal forces caused by operation of the planet carrier, said terms "radially" and "centrifugal" being defined as being radially and centrifugal relative to the main central rotation axis.".

In the following, the invention is further elucidated with reference to non-limiting embodiments and with reference to the schematic figures in the attached drawing, in which the following is shown.

Fig. 1 shows a disassembled exploded perspective view of an example of an embodiment of a planet carrier according to the invention, in combination with a corresponding plurality of planet gears being

assemblable to the planet carrier.

Fig. 2 shows the situation of Fig. 1 in the same perspective view, however this time in assembled condition.

Fig. 3 shows the situation of Fig. 1 in the same perspective view, however wherein this time only the rightmost part of Fig. 1, hereinafter "the second main part" of the planet carrier, is depicted.

Fig. 4 shows a side view onto the sole second main part of Fig. 3, wherein the side view is taken from the backside in Fig. 3, however wherein in Fig. 4 the side view is taken parallel to the axial direction of the planet carrier.

Fig. 5 shows a side view onto the whole, assembled planet carrier of Fig. 2, wherein the side view is taken from the backside in Fig. 2, however wherein in Fig. 5 the side view is taken parallel to the axial direction of the planet carrier.

The reference signs used in Figs. 1-5 are referring to the abovementioned parts and aspects of the invention, as well as to related parts and aspects, in the following manner.

I planet carrier

2 main central rotation axis

3 axial direction

4A-4C planetary central rotation axes

5A-5C planet gears

6A-6C planet axles

7A-7C stiffness-reducing slot-shaped interruptions

8A-8C lubricant-funnelling shape-discontinuities

II first main part

12 second main part

21 first carrying wall

22 second carrying wall 31A-31C first planet axle receiving areas

32 A- 32 C second planet axle receiving areas

41D-41F assembling walls of first main part

42D-42F assembling slots in second carrying wall

52 flange structure of second main part

53-56 further assembling means

Based on the above introductory description, including the above brief description of the drawing figures, and based on the above-explained reference signs used in the drawing, the shown example of Figs. 1-5 is for the greatest part readily self-explanatory. The following extra explanations are given.

In the shown example, the planet carrier 1 comprises the first main part 11 and the second main part 12, see Fig. 1. The first main part 11 comprises the first carrying wall 21, as well as the assembling walls 41D, 41E, 41F. The second main part 12 comprises the second carrying wall 22, as well as the flange structure 52. It is noted that the specific flange structure 52 of the second main part 12 is not essential or relevant for the present invention, and is therefore not further described herein.

The assembled condition of Fig. 2 is obtained from the

disassembled condition of Fig. 1 by inserting the assembling walls 41D, 41E, 41F of the first main part 11 into the assembling slots 42D, 42E, 42F

(indicated and best seen in Fig. 4) in the second carrying wall 22, while at the same time mounting the planet gears 5 A, 5B, 5C to the planet axles 6A, 6B, 6C by using the further assembling means 53, 54, 55, 56. In the assembled condition, the planet axles 6A, 6B, 6C are suspended from the first carrying wall 21 and from the second carrying wall 22 at the first planet axle receiving areas 31A, 31B, 31C and the second planet axle receiving areas 32 A, 32B, 32 C, respectively. In the shown example, these first and second planet axle receiving areas 31A, 31B, 31C, 32A, 32B, 32C are formed by defining-boundaries of holes in the first and second carrying walls 21, 22, respectively.

As mentioned in the above introduction, the first and second carrying walls 21 and 22 have "a first stiffness" and "a second stiffness", respectively, against deformation due to load transmitted by the planet axles 6A, 6B, 6C at the first and second planet axle receiving areas 31A, 31B, 31C and 32A, 32B, 32C, respectively, in radial directions relative to the planetary central rotation axes 4A, 4B, 4C, respectively.

The stiffness-reducing slot-shaped interruptions are indicated with their reference numerals 7 A, 7B, 7C in Figs. 3, 4. Especially in Fig. 4 it is clearly seen that each of the stiffness-reducing slot-shaped interruptions 7 A, 7B, 7C, as seen in the axial side view of Fig. 4, has a curved longitudinal slot direction having a U-shaped form which envelopes its corresponding planetary central rotation axis 4A, 4B, 4C, thereby reducing the absolute value of the difference between said first stiffness and said second stiffness as compared to the situation in which said plurality of stiffness-reducing slot-shaped interruptions 7 A, 7B, 7C would have been absent.

The lubricant-funnelling shape- discontinuities are indicated with their reference numerals 8A, 8B, 8C in Figs. 3, 4. Especially from Fig. 4 it clearly follows that the lubricant-funnelling shape- discontinuities 8A, 8B, 8C are on a radially inward side of the second planet axle receiving areas 32 A, 32B, 32 C, respectively. In the shown example, each lubricant- funnelling shape-discontinuity is a complete interruption of the shown second carrying wall 22, hence a completely through-going passageway through the second carrying wall 22. In the shown example, each lubricant- funnelling shape-discontinuity may be interpreted as being formed by two cutting-edges, wherein the more radially inward cutting edge has a larger radius of curvature than the more radially outward cutting edge. The more radially inward cutting edge takes care of "catching" centrifugally moved lubricant over a relatively wide circumferential range, while the more radially outward cutting edge takes care of funnelling the catched lubricant towards the second planet axle receiving area concerned. Accordingly, thanks to the application of such lubricant-funnelling shape-discontinuities, the amount of centrifugally moved lubricant not reaching the planet axles is reduced, while the amount of centrifugally moved lubricant that actually reaches the planet axles is increased.

While the invention has been described and illustrated in detail in the foregoing description and in the drawing figures, such description and illustration are to be considered exemplary and/or illustrative and not restrictive; the invention is not limited to the disclosed embodiments.

As an example, it is noted that it has been described herein that according to the invention: "each of said stiffness-reducing slot- shaped interruptions, as seen in axial side view along said axial direction, has a curved longitudinal slot direction having a U-shaped form which envelopes its corresponding planetary central rotation axis". The following notes are made in respect of the expressions "U-shaped" and "envelopes" as used herein.

The meaning of said expression "U-shaped", as used in the present document, may broadly refer to variously curved U- shapes, which among others may include various C-shapes, V-shapes, or the like. The expression "U-shaped" may include various shapes having continuous slopes, as well as various shapes having discontinuous slopes, as well as various shapes having combinations of continuous slopes and discontinuous slopes.

The meaning of said expression "envelopes", as used in the present document, may broadly refer to configurations in which, as seen in axial side view along said axial direction, the stiffness-reducing slot-shaped interruption is extending on diametrically opposite sides of the

corresponding planetary central rotation axis. For example, in the plane of Fig. 4 there are many possibilities to draw a single straight line through the planetary central rotation axis 4A, wherein this single straight line intersects the stiffness-reducing slot- shaped interruption 7A on opposite sides of the axis 4A.

As another example, it is noted that it has been described herein that according to the invention the second carrying wall has a plurality of "stiffness-reducing slot-shaped interruptions". The following notes are made in respect of such an "interruption" of the second carrying wall as used herein. The meaning of such an interruption of such a wall, as used in the present document, may broadly refer to a complete interruption of such a wall, hence a completely through-going passageway through the wall, or a thinned area of such a wall.

As yet another example, it is noted that it has been described herein that according to the invention at least one of the first carrying wall and the second carrying wall may have at least one "lubricant-funnelling shape-discontinuity". The following notes are made in respect of such an

"shape-discontinuity" of such a carrying wall as used herein. The meaning of such a shape- discontinuity of such a wall, as used in the present document, may broadly refer to a complete interruption of such a wall, hence a completely through-going passageway through the wall, or a thinned and/or thicked area of such a wall.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single item recited in the claims may fulfil the functions of several items recited in the claims. For the purpose of clarity and a concise description, features are disclosed herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include

embodiments having combinations of all or some of the features disclosed. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures can not be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A planet carrier for a planetary gear set, wherein the planet carrier (1) comprises:

- a main central rotation axis (2), about which a sun gear and a ring gear for such a planetary gear set are co-axially rotatable when assembled to the planet carrier (1), wherein an axial direction (3) of the planet carrier is defined as being parallel to said main central rotation axis, and;

- a plurality of planetary central rotation axes (4A, 4B, 4C), which are parallel to said axial direction, and about which a corresponding plurality of planet gears (5A, 5B, 5C), respectively, of such a planetary gear set are rotatable when assembled to the planet carrier (1);

- a first carrying wall (21) and a second carrying wall (22), which are extending transversely to said axial direction (3), and which are mutually spaced in said axial direction;

- a plurality of planet axles (6A, 6B, 6C) having said plurality of planetary central rotation axes (4A, 4B, 4C), respectively, and which are assemblable to, or integrally manufactured with, said corresponding plurality of planet gears (5A, 5B, 5C), respectively;

and wherein:

- the planet axles (6A, 6B, 6C) are extending in-between the first carrying wall (21) and the second carrying wall (22), as seen in said axial direction (3);

- the first carrying wall (21) has a plurality of first planet axle receiving areas (31A, 31B, 31C) where the respective planet axles (6A, 6B, 6C) are suspended from the first carrying wall, and the second carrying wall (22) has a plurality of second planet axle receiving areas (32 A, 32B, 32 C) where the respective planet axles (6A, 6B, 6C) are suspended from the second carrying wall;

- the first carrying wall (21) has a first stiffness against deformation due to load transmitted by the planet axles at the first planet axle receiving areas (31A, 31B, 31C) in radial directions relative to said planetary central rotation axes (4A, 4B, 4C), respectively; and

- the second carrying wall (22) has a second stiffness against deformation due to load transmitted by the planet axles at the second planet axle receiving areas (32 A, 32B, 32 C) in radial directions relative to said planetary central rotation axes (4A, 4B, 4C), respectively;

characterized in that

the second carrying wall (22) has a plurality of stiffness-reducing slot-shaped interruptions (7A, 7B, 7C) corresponding to said plurality of second planet axle receiving areas (32A, 32B, 32C), respectively,

corresponding to said planetary central rotation axes (4A, 4B, 4C), respectively, wherein each of said stiffness-reducing slot- shaped

interruptions, as seen in axial side view along said axial direction (3), has a curved longitudinal slot direction having a U-shaped form which envelopes its corresponding planetary central rotation axis (4A, 4B, 4C), thereby reducing the absolute value of the difference between said first stiffness and said second stiffness as compared to the situation in which said plurality of stiffness-reducing slot-shaped interruptions (7A, 7B, 7C) would have been absent.

2. A planet carrier according to claim 1, wherein at least one of the first carrying wall (21) and the second carrying wall (22) has at least one lubricant-funnelling shape-discontinuity (8A, 8B, 8C) on a radially inward side of at least one corresponding one, respectively, of the first planet axle receiving areas (31A, 31B, 31C) and the second planet axle receiving areas (32A, 32B, 32C), said lubricant-funnelling shape-discontinuity (8A, 8B, 8C) being configured for funnelling a lubricant towards at least one

corresponding one, respectively, of the planet axles (6A, 6B, 6C), when said lubricant is adhering to the first carrying wall (21) and/or the second carrying wall (22) concerned while said lubricant is being moved radially outward by centrifugal forces caused by operation of the planet carrier, said terms "radially" and "centrifugal" being defined as being radially and centrifugal relative to the main central rotation axis (2).

3. A planetary gear set comprising:

- a planet carrier (1) according to any one of the preceding claims; and

- a plurality of planet gears (5A, 5B, 5C), which are mounted to the planet carrier in a rotatable manner about said plurality of planetary central rotation axes (4A, 4B, 4C), respectively.

4. A drive unit for a vehicle, comprising:

- a planetary gear set according to claim 3; and

- a sun gear and a ring gear, which by engagement through said plurality of planet gears are co-axially rotatable about said main central rotation axis (2) of the planet carrier (1).