Patent Application
20230417290
The present application claims priority to German Patent App. No. DE 10 2022 206 419.4, to Alexander Mick, filed Jun. 27, 2022, the contents of which is incorporated by reference in its entirety herein.
The present disclosure relates to a tripod roller for a tripod joint assembly with the features recited in the independent claims. Furthermore, the present disclosure relates to a tripod joint with such tripod rollers.
Tripods roller comprising an outer ring with an annular running surface on its outer circumference for rolling in a tripod housing as well as an inner peripheral surface, an inner ring with an annular running surface on its inner circumference for mounting on a pin of a tripod star and an outer peripheral surface and opposite end faces, rolling elements, which are arranged in an annular space between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring and via which the outer ring is rotatably mounted with its inner peripheral surface on the outer peripheral surface of the inner ring, and axial locking rings, which are fixed to the outer ring and secure the outer ring axially relative to the inner ring, and corresponding tripod joints are known, for example, from DE 10 2009 041 086 A1 and DE 10 2020 212 991 A1.
Such tripod rollers and tripod joints are used, for example, in side shafts on the drive side of motor vehicles. Their main functions are the transmission of torque and power from the drive to the wheel as well as the bending and length compensation during simultaneous steering and spring movements as well as unit movements.
A generic tripod roller for a tripod joint is also generally known from JP 2019-124253 A. In order to improve the lubrication of the contact between the inner ring and the pin of the tripod star, it is proposed to form lubricant pockets on the end faces of the inner ring and on the insides of the axial locking rings. The purpose of these pockets is to store lubricant for shortage situations in order to lubricate the contact surfaces between the inner peripheral surface of the inner ring and the outer peripheral surface of the pin.
In generic tripod joints, high loads occur while the vehicle is being driven, particularly in the region of the tripod rollers. In electric vehicles, this is exacerbated by increased torques and increased alternating loads that result from the recuperation.
Particularly in the case of the aforementioned double rollers with an outer ring and an inner ring and rolling elements arranged between them, there can be significant wear between the outer ring and the rolling elements and also between the inner ring and the rolling elements.
This can be remedied by a correspondingly more generous dimensioning of the components. This leads to large joint sizes, however, which should be avoided as much as possible with regard to the usually very narrow installation spaces in modern vehicles.
The use of alternative lubricants could be considered as well. Practical tests have shown, however, that it is not possible to achieve any substantial service life improvement in this manner.
Against this background, aspects of the present disclosure are directed to creating tripod rollers of the aforementioned type, which have an improved service life, a compact design, and are able to withstand high loads.
Some aspects are disclosed by a tripod roller according to the independent claims. This tripod roller may be configured such that the inner ring has recesses on at least one of its end faces for receiving lubricant, with the recesses on the outer peripheral surface of the inner ring opening into the annular space in which the rolling elements are arranged in order to supply the rolling elements with lubricant.
It has been shown that the service life can be significantly improved in this manner. Despite the practical encapsulation of the annular space by the axial locking rings, the recesses achieve an improved supply of lubricant to the contact points of the rolling elements with the inner ring and the outer ring.
As a result, the use of larger joint sizes can be avoided, which also reduces weight.
The recesses can be realized without any great additional effort in terms of production technology. These recesses, can, for example, be taken into account when designing the inner ring, which is usually forged.
Special embodiments of the present disclosure are the subject of the dependent claims.
The present disclosure is explained in more detail below using an embodiment illustrated in the drawing and further modifications. The drawing shows in:
For a better understanding of the principles of the present disclosure, embodiments of the present disclosure will be explained in more detail below with reference to the figures. It is to be understood that the present disclosure is not limited to these embodiments and that the features described may be combined or modified without departing from the scope of the present disclosure as defined in the appended claims.
In some examples disclosed herein, the bearing length of the rolling elements in the axial direction is smaller than the length of the inner ring on its outer peripheral surface in the axial direction. In addition, the depth of the recesses on the end face at their respective opening into the annular space can be smaller than the difference between the length of the inner ring and the bearing length. As a result, the strength and acoustic properties of the tripod roller remain largely unaffected by the recesses.
If the axially opposite end faces of the inner ring are each provided with recesses, it may be advantageous to select the depth of the recesses on the end face at their respective opening into the annular space such that it is less than half the difference between the length of the inner ring and the bearing length.
In some examples, the recesses on the end face of the inner ring open into the inner peripheral surface of the inner ring, as a result of which a channel for transporting the lubricant is provided over the entire end face. The recesses on the end face of the inner ring may be configured as grooves with a constant cross-section in the longitudinal direction of the respective groove.
In some examples, the recesses on the end face of the inner ring may be deeper on the end face at their opening into the annular space than at their opening into the inner peripheral surface of the inner ring. Also, the recesses on the end face of the inner ring can be configured as grooves which are deeper at their opening into the inner peripheral surface of the inner ring than at their opening into the annular space. Furthermore, the width of the grooves may decrease from the opening into the inner peripheral surface of the inner ring to the opening into the annular space.
In some examples, the recesses on the end face of the inner ring may be configured as pockets that only open into the annular space, which means that they have no opening into the inner peripheral surface of the inner ring. The pockets preferably extend radially inwardly from the outer peripheral surface of the inner ring to only half or up to two-thirds of the inner ring thickness.
In some examples, the recesses can be designed as grooves connecting the annular space with the inner peripheral surface of the inner ring, which are curved in an arc shape in relation to a radial direction of the inner ring. Such an approximately paddle-wheel-shaped configuration leads to a rotary movement of the rollers and results in an active conveying effect of the lubricant and thus a good supply of the lubricant to the rolling elements. When a motor vehicle is being driven, the tripod rollers perform a continuous oscillating rolling motion. A relative rotating movement takes place between the outer ring and the inner ring, which results in the conveying effect. Furthermore, the curvatures of the grooves on the opposing end faces may be opposite each other. Depending on the direction of rotation, such an inverse design means that lubricant is supplied on one side and “used” lubricant is discharged or pumped out of the rolling element contact on the other side.
In some examples, recesses for accommodating lubricant are formed on the axial locking ring on an inner side facing towards the inner ring, in order to convey lubricant more effectively to the rolling elements. The recesses on the axial locking ring can, for example, include radial grooves that extend radially from an inner edge of the axial locking ring at least up to the level of the annular space. For example, these radial grooves can extend continuously over the entire end face of the axial lock or as a pocket only up to the middle or the last third of the ring height.
Furthermore, the recesses may include axial grooves on the axial locking ring, which open into the annular space and are formed obliquely or axially running on the inner edge of the axial locking ring. The radial grooves and the axial grooves may be provided together on an axial locking ring and can preferably, but not necessarily, be connected to one another.
The tripod roller may be configured for a tripod joint assembly that includes a tripod star with radially projecting pins, with a tripod roller of the type explained above being mounted on each pin, and a tripod housing with a pair of tracks for each tripod roller to guide the annular running surface of the outer ring of the respective tripod roller.
Such a tripod joint is characterized by a compact design and a long service life. It is particularly suitable for the high torques and alternating loads that occur in electric vehicle drives.
The tripod joint assembly 1 may include an inner joint part in the form of a tripod star 10 with an axis of rotation A and an outer joint part in the form of a tripod housing 20 with an axis of rotation B. Pairs of tracks 21 are formed on the inside of the outer joint part, in which the inner joint part is guided axially, i.e., in the direction of the axis of rotation B. When the tripod joint assembly 1 is extended, the axes of rotation A and B are aligned with one another. If the tripod joint assembly 1 is bent during operation, however, the axes of rotation form a bending angle that is not equal to 0°, as is shown in
The tripod star 10 may be configured with a central shaft portion 11 and a plurality of, preferably three, pins 12 protruding from the shaft portion 11. The central shaft portion 11 can be designed as a ring body that can be coupled to a shaft.
The pins 12 may be configured in the circumferential direction at the same distance from one another about the axis of rotation A of the inner joint part or tripod star 10. Their longitudinal axes Z run substantially radially to the axis of rotation A and preferably lie in a common plane, as shown in the embodiment illustrated in
Furthermore, the tripod joint assembly 1 may include a tripod roller 30 on the tripod star 10 for each pin 12 that is rotatably mounted on the associated pin 12 of the tripod star 10 about the longitudinal axis Z of the pin 12.
In some examples, the pins 12 each have a profiled surface 13 for mounting the tripod rollers 30, which is explained in more detail below.
Each tripod roller 30 may include an outer ring 31 and an inner ring 32 as well as rolling elements 33 arranged between them, so that the outer ring 31 and the inner ring 32 can be rotated in relation to one another.
The outer ring 31 and the inner ring 32 are preferably designed as rotationally symmetrical components.
For example, the outer ring 31 has an annular running surface 31a on its outer circumference for rolling on a pair of tracks 21 of the tripod housing 20, and also an inner peripheral surface 31b.
On its inner circumference, the inner ring 32 has an annular running surface 32a to be placed on the pin 12 of the tripod star 10, as well as an outer circumferential surface 32b and opposite end faces 32c and 32d.
The rolling elements 33, which are preferably designed as needles or rollers, are arranged in an annular space 34 between the inner peripheral surface 31b of the outer ring 31 and the outer peripheral surface 32b of the inner ring 32. The annular space 34 extends around the pin 12. The inner peripheral surface 31b of the outer ring 31 is rotatably mounted on the outer peripheral surface 32b of the inner ring 32 via the rolling elements 33. Preferably, the rolling elements 33 each have a line contact with the inner peripheral surface 31b of the outer ring 31 and with the outer peripheral surface 32b of the inner ring 32.
Furthermore, axial locking rings 40 are provided, which are fixed to the outer ring 31 and which axially secure the outer ring 31 relative to the inner ring 32. The axial locking rings 40 are radially slotted for assembly and have, for example, a rectangular cross section. They are fitted into corresponding grooves on the inner peripheral surface 31b of the outer ring 31.
In some examples, annular space 34 is closed by the inner sides 40a of the axial locking rings 40 arranged axially on both sides of the annular space 34. The axial locking rings 40 also ensure that the rolling elements 33 cannot migrate sideways out of the annular space 34.
As shown in the examples of
As a result, the contact length 1W of the rolling elements 33 is smaller in the axial direction than the length 1IR of the inner ring 32 on its outer peripheral surface 32b in the axial direction.
Each tripod roller 30 can roll with the annular running surface 31a of its outer ring 31 along a pair of tracks 21 of the outer joint part or tripod housing 20. For this purpose, the profile of the ring-shaped running surface 31a can be convexly curved outwards in the cross-section. The tracks of the pair of tracks 21 can correspondingly have a concave cross-sectional profile, as can be seen in
Due to the convex configuration of the surface 13 of the pin 12 with which the inner peripheral surface 32a of the inner ring 32 is in contact, the inner ring 32 can be tilted relative to the longitudinal axis Z of the associated pin 12 when the tripod joint assembly 1 is tilted. In addition, there is an axial displaceability in the direction of the longitudinal axis Z of the pin 12.
The functions of the rotation about the pins 12, the tilting as well as the axial displacement can also be realized in other ways. The embodiment of a rotatable bearing in a plurality of directions shown in
The outer joint part or tripod housing 20 has its own engagement portion for each tripod roller 30. The engagement portion is designed, for example, like a sleeve and can have a constant cross-sectional profile over its axial length.
In the embodiment illustrated in
The profiling of both the tracks 21 on the tripod housing 20 and the annular running surfaces 31a of the outer rings 31 of the tripod rollers 30 have the effect that, when the joint 1 rotates and the component axes A and B bend towards one another, the tripod rollers 30 are moved back and forth parallel to the axis of rotation B of the tripod housing 20. As has already been explained above, the degree of pivoting freedom required for this can be provided, for example, between the pins 12 and the inner rings 32 of the tripod rollers 30.
To improve the service life of the tripod rollers 30, as shown in
In further variants, as shown by way of example in
Both measures, namely recesses 35 on the inner ring side and recesses 41 on the axial locking ring side, can be combined with one another. In the present case, the recesses 35 and 41 are preferably depressions in the respective surfaces 32c, 32d and 40a and 43.
Particularly suitable embodiment variants in this respect will be explained in more detail below, without the present disclosure being restricted to these specific variants. In particular, combinations of the following design variants can also be implemented, so that recesses 35 or 41 of different design variants are provided on an inner ring 32 and/or an axial locking ring 40.
As can be seen in particular from
As a modification of this, the depression t of the recesses 35 in the end face 32c, 32d at their respective opening into the annular space 34 can also be selected, particularly if only one end face 32c, 32d is to be provided with recesses 35, but also in general, such that it is smaller than the difference between the length 1IR of the inner ring 32 and the bearing length 1W.
It is also possible to make the depressions t of the recesses 35 even deeper than mentioned above and to thereby accept a locally reduced contact length between the inner ring 32 and the rolling elements 33. The effective bearing length 1W of the rolling elements 33 is restricted by the deeper depression. This is acceptable as long as, in terms of the service life, the advantage of an improved supply of lubricant outweighs the disadvantage of the reduced bearing length.
The recesses 35 can, for example, be deeper at their opening into the inner peripheral surface 32a of the inner ring 32 than at their opening into the annular space 34. As can be seen in particular in
In a modification of this, the recesses 35 on the end face 32c, 32d of the inner ring 32 can be deeper on the end face 32c, 32d at their opening into the annular space 34 than at their opening into the inner peripheral surface 32a of the inner ring 32. In this case, t1 is greater than t2.
In addition, as can be seen in particular from
These two measures—different depths on the one hand and different width on the other—can be implemented in combination, but also independently of one another.
Another design feature for the recesses 35 is shown in
As can be seen in
In the viewing direction perpendicular to the end face 32c, the recesses 35 are designed in the shape of a paddle wheel. When the tripod rollers 30 rotate, this causes an active conveying effect for the lubricant. Since the tripod rollers 30 perform a continuous oscillating rolling movement when the vehicle is being driven, there is a constant relative rotating movement between the outer ring 31 and the inner ring 32, which facilitates the conveying effect for the lubricant so that lubricant can be introduced into the annular space 34 from the outside.
If the paddle-wheel-shaped recesses 35 are designed in opposite directions on an inner ring 32 on the two opposite axial end faces 32c and 32d, one side supplies lubricant and the other side removes lubricant, depending on the direction of rotation. This allows for a very good supply of lubricant to the rolling elements 32 and their contact points with the outer ring 31 and the inner ring 32.
As already mentioned, the configuration of the grooves 36, which are shown in
It is also possible, as a modification of the illustration in
In the fifth embodiment variant, these recesses 41 are formed on a side 40a of the axial locking ring 40 pointing toward the inner ring 32 in order to effectively convey lubricant to the rolling elements 33.
In the present case, these recesses 41 on the axial locking ring 40 comprise radial grooves 42 which extend radially from an inner edge 43 of the axial locking ring 40 at least up to the level of the annular space 34.
In
However, it is also possible, as shown in a sixth embodiment variant in
Furthermore, the recesses 41 on the axial locking ring 40 can comprise axial grooves 44, as shown in a seventh embodiment variant in
The radial grooves 42 and the axial grooves 44 can be provided together on an axial locking ring 40. In this case, these can optionally be connected to one another. However, it is also possible to arrange them unconnectedly next to one another.
It has been shown that the above-described modifications to the tripod roller 30 can improve the service life of a tripod joint assembly 1 in a surprisingly significant way without increasing the weight of the component or the external dimensions. This way, compact tripod joints 1 with high loads can be realized.
Due to the improved service life properties, the tripod joints explained above are particularly suitable for motor vehicles with an electric drive and comparable drive conditions with high torques and strong alternating loads. The strength and acoustic properties of the tripod rollers 30 remain unaffected.
The modification according to the present disclosure can also be realized without undue additional technical effort.
The formation of recesses 35 on the inner ring 32, for example, can be integrated into a forging process. In this case, the additional manufacturing effort remains minimal, since only the forging tool has to be adapted.
The formation of additional recesses 41 on the axial locking ring 40 can be realized very easily with an additional step in the stamping process for the axial locking ring 40.
The present disclosure was explained in more detail above using an exemplary embodiment and further modifications. In particular, individual technical features that have been explained above in the context of other individual features can be realized independently of these and in combination with other individual features, even if this is not expressly described, as long as it is technically possible to do so. The present disclosure is therefore expressly not limited to the exemplary embodiments and modifications described, but rather includes all configurations defined by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022206419.4 | Jun 2022 | DE | national |
