NL2019488B1

NL2019488B1 - Improved planet carrier.

Info

Publication number: NL2019488B1
Application number: NL2019488A
Authority: NL
Inventors: Verpoorten Roel; Tits Wouter; Aerts Rudi
Original assignee: Punch Powertrain Nv
Priority date: 2017-09-06
Filing date: 2017-09-06
Publication date: 2019-03-14
Also published as: WO2019048568A1; CN111247361B; CN111247361A; DE112018004901T5

Abstract

A planet carrier comprises a plurality of planet axles suspended in-between a first carrying wall and a second carrying wall (22). The second carrying wall (22) has a plurality of stiffness-reducing slot-shaped interruptions (7A, 7B, 7C) corresponding to a plurality of second planet axle receiving areas (32A, 32B, 32C). Each of the stiffness-reducing slot-shaped interruptions has a curved longitudinal slot direction having a U-shaped form which envelopes a planetary central rotation axis (4A, 4B, 40). Thanks to these special stiffness-reducing slot-shaped interruptions, improved mutual balancing of the stiffnesses of both carrying walls is obtained. This results into improved gear meshing under load.

Description

Title: 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 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 slotshaped 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 slotshaped 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 shapediscontinuities 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 lubricantfunnelling 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 main central rotation axis, about which a sun gear and a ringgear 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;

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.

1	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
11	first main part
12	second main part
21	first carrying wall
22	second carrying wall

31A-31C first planet axle receiving areas 32A-32C second planet axle receiving areas

41D-41F assembling walls of first main part

42D-42F assembling slots in second carrying wall 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 4ID, 4IE, 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, 4IF 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 5A, 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, 3 IB, 31C and the second planet axle receiving areas 32A, 32B, 32C, 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, 3IB, 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 7A, 7B, 7C in Figs. 3, 4. Especially in Fig. 4 it is clearly seen that each of the stiffness-reducing slot-shaped interruptions 7A, 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 7A, 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 32A, 32B, 32C, respectively. In the shown example, each lubricantfunnelling 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 lubricantfunnelling 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 usedin 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 7 A 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

Conclusions

1. A planetary gear carrier for a planetary gear set, the planetary gear carrier (1) comprising:

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

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

- a first supporting wall (21) and a second supporting wall (22), which extend transversely to said axial direction (3), and which are spaced apart in said axial direction;

multiple planetary axes (6A, 6B, 6C) with said plurality of central planetary rotation axes (4A, 4B, 4C), respectively, and which assemble) or are integrally manufactured with, respectively, said associated plurality of planetary gears (5A, 5B , 5C);

and where:

- the planet support shafts (6A, 6B, 6C) extend between the first support wall (21) and the second support wall (22), as viewed in said axial direction (3);

the first bearing wall (21) has a plurality of first planetary wheel axle receiving areas (31A, 31B, 31C) where the respective planetary axle shafts (6A, 6B, 6C) are suspended from the first bearing wall, and the second bearing wall (22) has a plurality of second planetary wheel axle receiving areas (32A, 32B , 32C) where the respective planet carrier shafts (6A, 6B, 6C) are suspended from the second bearing wall;

- the first bearing wall (21) has a first stiffness against deformation due to load transmitted by the planetary carrier axes at the location of the first planetary wheel receiving areas (31A, 31B, 31C) in radial directions with respect to said central planetary rotation axes (4A, respectively) , 4B, 4C); and

- the second bearing wall (22) has a second stiffness against deformation due to load transferred by the planet carrier axes at the location of the second planet wheel axle receiving areas (32A, 32B, 32C) in radial directions with respect to said central planet rotation axes (4A, respectively) , 4B, 4C);

characterized in that the second bearing wall (22) has a plurality of stiffness-reducing slotted interruptions (7A, 7B, 7C) associated with said plurality of second planet gear axis receiving areas (32A, 32B, 32C) associated with said central planet rotation axes (4A, respectively), 4B, 4C), wherein each of said stiffness reducing slit breaks, as viewed in axial side view along said axial direction (3), has a curved longitudinal slit direction with a U-shaped shape enclosing its associated central planetary rotation axis (4A, 4B, 4C), whereby the absolute value of the difference between said first stiffness and said second stiffness is reduced compared to the situation where said multiple stiffness reducing slit breaks (7A, 7B, 7C) would be absent.

A planetary gear carrier according to claim 1, wherein at least one of the first bearing wall (21) and the second bearing wall (22) has at least one "funnel-flowing lubricant" shape discontinuity (8A, 8B, 8C) at a radial inward side of, respectively, at least one associated one of the first planetary gear axle receiving areas (31A, 31B, 31C) and the second planetary gear axle receiving areas (32A, 32B, 32C), said "lubricant as funnel-flowing" mold continuity configured to flow a lubricant to, respectively, at least one associated one of the planet carrier shafts (6A, 6B, 6C), when said lubricant hangs from the respective first supporting wall (21) and / or the second supporting wall (22) while said lubricant is moved radially outward by centrifugal forces caused by operation of the planetary gear carrier, said terms "radial" and "centrifugal" being defined as being radial and centrifugal with respect to the central main rotation axis (2).

3. A planetary gear set comprising:

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

a plurality of planet wheels (5A, 5B, 5C), which are mounted on the planetary wheel carrier in a rotatable manner around, respectively, said plurality of central planetary rotation axes (4A, 4B, 4C).

A vehicle drive unit, comprising:

- a planetary wheel set according to claim 3; and

- a sun wheel and a ring wheel, which are co-axially rotatable around said central main rotation axis (2) of the planet wheel carrier (1) by engagement via said plural planet wheels.

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