Patent Application
20190368551
A variety of rotating boots of the type specified above are known from the prior art. As such, WO 2009/1555955 A1 discloses a rotating boot attached to a slip joint that is supposed to have improved properties when subjected to centrifugal forces, in particular with regard to the lubricant pressure then acting on the rotating boot. For this, a specific geometry is proposed between a transition region and a membrane region, and in particular the placement of external radial fins that bridge the transition region and are connected to a surface of a first membrane component of the membrane region. The boot disclosed therein is intended to reduce lubricant pressure, and does not need internal reinforcement fins due to its specific geometry, as was previously known from the prior art, as disclosed in WO 2009/155955 A1.
WO 2013/170867 A1 discloses a further development of the rotating boot according to WO 2009/155955 A1, with an improved stability. This is achieved by a specific configuration of the diameters of the transition region to those of the membrane region. There can also be outer radial fins in the transition region, similar to those disclosed in WO 2009/155955 A1.
The requirements for rotating boots in modern gearings or joint assemblies for utility and motor vehicles have increased, in particular with respect to the stability thereof at high rotational rates. In particular because of the increase in electric vehicles and the alternative drive systems used in automobiles, in particular with regard to the use of electric motors, higher rotational rates are obtained, such that rotating boots must withstand the further increased centrifugal forces resulting from higher rotational rates. These forces act on the lubrication in the boot, the so-called grease load, as well as on the boot material itself. There are various problems with the boots known from the prior art high rotational rates. In particular, the boot is stretched out in the transition regions, in particular as a result of the grease load, and the membrane region becomes deformed. The latter results in a reduced service life due to material wear. The stretching in the transition region in particular can also lead to undesired contact with adjacent components, as well as a reduced lubrication of adjacent joint components, in particular slip joints, including universal joints. In addition, the rotating boot normally bearing on the joint housing erodes in the region of a joint housing edge, in the proximity of the first fastening regions of the rotating boots, which face toward the joint housing.
A rotating boot has at least a first fastening region, a second fastening region, a transition region adjacent to the first fastening region, and an adjoining membrane region. A universal joint, a shaft, and a joint assembly can have such a boot. Improvements to the rigidity of the boots known from the prior art result, such that they can satisfy the requirements placed thereon, in particular with regard to the service lives thereof, as well as for obtaining a sufficient lubrication of a joint, even at high rotational rates.
A rotating boot of the type specified in the above can have at least one, e.g., exactly one, circumferential reinforcement fin on an outer surface of the transition region. There can be exactly one reinforcement fin. The circumferential reinforcement fin can form a closed ring on the outer surface of the transition region. If there are two or more reinforcement fins, they can be parallel to one another on the outer surface of the transition region. The inventors have realized that with high rotational rates, a boot with a grease load is substantially subjected to tangential forces. These tangential forces cannot be deflected by the radial outer fins known from the prior art, and instead, at high rotational rates, they are simply displaced outward, without improving the radial rigidity of the rotating boot. An increase in the wall thickness of the rotating boot that would also improve the radial rigidity, would result in higher production costs, as well as a potentially reduced quality of the rotating boot. Increased costs can also be expected with the use of reinforcement fibers, in particular those oriented tangentially, in the rotating boot material. As an alternative, both in terms of the machining as well as the production costs, the inventors have arrived at the solution of placing at least one circumferential reinforcement fin on the outer surface of the transition region. The tangential forces are intercepted by this at least one reinforcement fin, even at high rotational rates, such that ultimately, the radial rigidity of the rotating boot is improved at high rotational rates.
In an example, the reinforcement fin on a wall portion of the transition region is substantially perpendicular to an inner surface of the wall portion. The reinforcement fin can also be referred to as being perpendicular to an upper surface of a binding seat region in the first fastening region. The at least one reinforcement fin itself has an upper surface and a lower surface, which are also preferably angled slightly toward one another. The angle can be in a range of approximately 0.5° to approximately 10°, or in a range of approximately 1° to approximately 7.5°.
In another example, the at least one reinforcement fin is displaced on the transition region toward a first subsection of the membrane region. The membrane region comprises the first sub-region, adjacent to the transition region, and an adjacent second membrane part, which can be referred to as trough-like. The first membrane part and the second membrane part are connected to one another by a rounded part, wherein the rounded part forms a type of circumferential peak in the manner of a bellows when the boot is viewed from above. The closer the at least one reinforcement fin, preferably exactly one reinforcement fin, is to the membrane region, and thus the first membrane part, i.e. the smaller the diameter of the at least one circumferential reinforcement fin is, the lower the centrifugal forces are that affect it, such that it is possible to reduce the tangential forces acting on it. In particular, a height h1 between an upper surface of the first membrane part facing the first reinforcement fin, preferably exactly one reinforcement fin, adjacent thereto, and a lower surface of the reinforcement fin, is less than a height h2 between a lower surface of an excess material of the first fastening region, if there is any, or a lower surface of the first fastening region, if there is no excess material, and an adjacent upper surface of at least one reinforcement fin facing it, preferably exactly one reinforcement fin. These heights h1 and h2 are determined directly on the outside of the transition region. The excess material has, in addition to its lower surface, an upper surface, which preferably contains a second positioning element of the first fastening region. The upper surface of the excess material can be substantially flush with an upper surface of the first binding seat region. The excess material also can have an end surface between the lower surface and upper surface. The end surface can transition smoothly, i.e. without steps, into an end surface of a radial fin, as shall be explained in greater detail below, and in particular, it can form a surface therewith that is flat and without irregularities. The ratio of the heights h1:h2 to one another can be in a range of approximately 0.2 to approximately 0.9, or in a range of 0.58 to approximately 0.88.
The transition region in the rotating boot comprises the wall portion and the at least one reinforcement fin located on the outside of the transition region. The transition region transitions directly into the membrane region, in that the first membrane part preferably adjoins the wall portion directly. The connection therebetween can be formed by the same material.
On the side facing away from the membrane, the transition region is bordered by the first fastening region, in particular by a lower surface of a binding seat region comprised in the first fastening region.
In another example of the present invention, an angle α is formed in a range of 0° to approximately 25°, preferably in a range of approximately 1.5° to approximately 22°, or in a range of approximately 2° to approximately 20°. As a result of this angle, the size in the region of the membrane part in particular can be reduced, such that with higher rotational rates, contact can be avoided with adjacent components when the membrane region stretches.
When the terms “approximately” or “substantially” are used in the present invention with respect to values, value ranges, or terms containing values such as “perpendicular,” these are to be understood to mean that which a person skilled in the art in the given context would regard as normal from an expert perspective. In particular, deviations to the given values, value ranges or terms containing values, of ±10%, preferably ±5%, or ±2% are comprised in the terms “approximately” and “substantially.”
In another example there are numerous supporting fins located between the at least one reinforcement fin and a first membrane part of the membrane region. There can be at least ten, or at least twenty, or at least thirty, and or at least forty supporting fins. These supporting fins engage with the lower surface of at least one reinforcement fin dedicated and adjacent to the first membrane part of the membrane region, and can extend beyond the lower surface of this reinforcement fin in another example, such that a ledge is formed. A smooth, i.e., continuous, transition between this reinforcement fin and the supporting fins is possible, however, seen in a cross section along a central axis of the rotating boot. End surface of the reinforcement fins and the supporting fins can transition into one another without steps, but a step can also be there formed. The supporting fins engage with the upper surface of the first membrane part facing the adjacent reinforcement fin, possibly over the entire surface thereof, extending radially outward. Possibly a transition of the reinforcement fins into the membrane region is smooth, i.e., continuous, seen in a cross section. The transition can be in the region of the first membrane part and/or the rounded part of the membrane region adjacent thereto. In another possible example, the height h1 defined above, which also defines a height of the supporting fins, is as low as possible. The ratio of the heights to one another can be in the ranges defined above. As a result, the heights h1 of the supporting fins are not very high, such that their weight is reduced, in particular with regard to the number of supporting fins located on the rotating boot, and they also exhibit a sufficient rigidity, such that they only exhibit a slight bending behavior between the first membrane part and the reinforcement fin adjacent thereto at high rotational rates. If there are two or more reinforcement fins, the supporting fins described above can also be formed between them.
In another example of the rotating boot, the supporting fins and the at least one reinforcement fin are substantially perpendicular to one another. This has a positive effect on the bending behavior of the supporting fins, i.e. their tendency to bend at higher rotational rates is further reduced.
In another example of the rotating boot, there are numerous radial fins located above the at least one reinforcement fin. In the present context, “above” refers to a region located above the reinforcement fin, delimited at one side by an upper surface of the at least one reinforcement fin. With numerous reinforcement fins, the term “above” refers to the region of an upper surface of that reinforcement fin that is closest to the first fastening region. In one example, the lower surface of the excess material of the first fastening region is adjacent to the upper surface of the reinforcement fin. The height h2 of the region above this reinforcement fin is defined above. A transition between the at least one reinforcement fin and the numerous radial fins can be smooth, i.e. continuous, seen in a cross section, such that there are no steps here, in particular. A design with steps, i.e., an uneven design, is also possible. The transition of the radial fins to an excess material of the first fastening region can be smooth, i.e., continuous, as is the present case, such that there are no steps. The radial fins can be located beneath the excess material. They can be connected to a lower surface of the excess material. The radial fins also possibly do not extend beyond an end surface of the excess material. The radial fins also possibly form a common plane with their outer edges, or end surfaces, without steps, with the end surface of the excess material. Here as well, a design with a step, i.e., a non-continuous design, is also a possibility. With an uneven design such as this, the radial fins extend beyond an outer edge of the excess material and/or the at least one reinforcement fin. There can be at least ten, or at least twenty, and or at least thirty radial fins. There can be for example twice as many radial fins as supporting fins. The ratio of the number of radial fins to supporting fins lies in a range of approximately 0.2 to approximately 0.8, or in a range of approximately 0.3 to approximately 0.7, and or in a range of approximately 0.4 to approximately 0.6.
In another example, the supporting fins and the radial fins are substantially flush to one another. This means that they form, together with the at least one reinforcement fin, a common outer edge, or end surface. This common outer edge or end surface can be smooth, i.e. continuous, i.e., it has no steps. This common outer edge or end surface, formed by supporting fins, the at least one reinforcement fin, and radial fins, can also have steps. The common outer edge or end surface of the at least one reinforcement fin, the radial fins, and the supporting fins, can be curved, i.e. forms an arc segment. The common outer edge or the respective end surfaces of the various fins can also be uneven. The supporting fins and radial fins do not have to be flush with one another. In this case, they are then offset to one another on the outer surface of the transition region of the rotating boot. Their outer edges or end surfaces can either be continuous, or they can transition with a step into a corresponding end surface of the circumferential reinforcement fin.
A length of the at least one reinforcement fin, seen in a cross section, and determined starting from an outer surface of the wall portion, can vary in different regions. The maximum length is basically limited by a maximum length of the first membrane part, or a height of the membrane part, determined between the inner surface of the wall portion of the transition region and a tangent to the rounded part of the membrane section that is parallel thereto. The at least one reinforcement fin can have a length that is approximately 0.3× to approximately 0.9×, or 0.5× to approximately 0.8× the length of an upper surface of the first membrane part. A maximum width of the supporting fins, seen in a cross section, is delimited by a tangent to the rounded part of the membrane region that is parallel to the inner surface of the wall section of the transition region. A maximum width of the radial fins, seen in a cross section, can be delimited by the maximum length of the at least one reinforcement fin.
The first fastening region can have excess material. The excess material can comprise a sub-region of the first binding seat region, as well as an outer positioning element in the first fastening region, which represents a border for a binding element located in the binding seat region. Because the excess material is connected at its lower surface to radial fins, and is thus supported by the radial fins, a bending away of the rotating boot in the region of a joint housing edge is hampered, if not altogether prevented, such that the radial rigidity is further increased. The excess material relates to the region of the first fastening region that extends beyond the wall region with respect to the inner surface of the wall portion of the transition region, and thus with respect to a joint housing edge that bears on the inner surface of the wall region.
In an alternative example, the first fastening region has no excess material. A second positioning element in the proximity of the membrane region is then located in the first fastening region, displaced toward the at least one first positioning element, and together with the first positioning element defines the first binding seat region. Such a configuration is preferred if the at least one second positioning element is to be placed in the region of the excess material in the example described above. A binding element, by means of which the rotating boot can be attached to a joint housing via the first fastening region and the first binding seat region, can be placed between the at least one first and the at least one second positioning element. In another alternative example, the at least one second positioning element can be omitted, since its positioning function is assumed by numerous radial fins. Not all of the radial fins need to assume such a positioning function, but it is possible that all of the radial fins assume a corresponding positioning function. With this type of design, the positioning fins extend beyond an upper surface of the first binding seat region, and have a bearing or positioning surface, which faces the first binding seat region, and thus the at least one first positioning element, thus also defining a first positioning region. They can also bear on the binding element, but this is not necessary. The at least one first positioning element can be in the shape of an ear, in corresponding to the description above. The bearing, or positioning, surface provided by the radial fins can be substantially rectangular. In particular with such an example that has numerous radial fins, at least some of which form a bearing surface, which can also be referred to as a positioning surface for placing a binding element in the first binding seat region of the first fastening region, the height h2 is determined starting from an lower surface of the first fastening region, and a surface of that reinforcement fin that is closest to the first fastening region.
The first binding seat region can have different designs. It can have a substantially flat upper surface. There can also be fin elements on the upper surface, in particular in the form of circumferential fins, preferably at least two, or at least three, four, five or more, in particular circumferential, fin elements that are adjacent to one another. The extend over the upper surface of the first binding seat region. In particular when closing a first binding element in the first binding seat region, these fin elements, or circumferential fins, improve the distribution of the closing force through the material of the first fastening region. The lower surface of the first fastening region of a rotating boot can also have different forms. They can be entirely flat, such that the lower surface and the upper surface are parallel to one another over the entire first binding seat region. There can be material accumulations on the lower surface of the first fastening region, however, preferably at least one, or at least two. These material accumulations can correspond to a circumferential groove located on a joint housing outer component that accommodates the at least one material accumulation on the lower surface of the first fastening region, possibly beneath the binding seat region.
A slip joint, possibly a universal slip joint, can have at least one boot as disclosed herein. Further, a shaft that has at least one boot as disclosed herein. The boot can be pre-assembled on the shaft, and or tensioned thereto. Further, a joint assembly can comprise at least one boot, at least one slip joint, and one shaft.
These and other advantages shall be explained in greater detail based on the following figures. Therein:
It should first be noted that the examples shown in the figures are not limiting. Instead, the features described therein can be combined with one another and with the features described above to obtain further examples. There can thus also be fewer or more radial fins or fewer or more supporting fins, and in particular not just one, but numerous circumferential reinforcement fins. There can thus be, for example, two substantially parallel circumferential reinforcement fins, between which there can also be supporting fins, although this is not necessary. The first and second fastening regions can also have different designs, and do not need to have opposing positioning elements for defining a first or second binding seat region. Instead, there can also be other elements, such as circumferential fins, etc. The reinforcement fins and the supporting fins and/or radial fins also do not need to be flush to one another, such that they form a common outer edge or end surface. In particular, the geometric design of the membrane region can also be different. It should also be noted that the reference symbols in the descriptions of the figures do not limit the claims, but only refer to the examples shown in the figures.
In general, the rotating boot can be made of a number of different materials. These can be selected from a group comprising thermoplastic elastomers that have a basis of polyurethane (TPU), polyamide (TPA), polyolefin (TPO), polyester (TPEE), a thermoplastic elastomer vulcanizate (TPV), or a thermoplastic polyether ester elastomer (TEE). The boot material can also contain other additives, in particular additives for promoting diffusion, etc. Alternatively, an elastomer material can also be used for the boot material, although thermoplastic elastomer materials are preferred. A known thermoplastic elastomer material for the production of boots is known by the brand name “Hytrel” from DuPont. Mixtures of different thermoplastic elastomers, or elastomer materials can also be used. The rotating boot can be produced in an injection molding process.
The rotating boot 10 has a second fastening region 14 with a smaller diameter than the first fastening region 12. This fastening region is otherwise similar to the first fastening region 12, and has opposing, ear-shaped third and fourth positioning elements 28, 30, and a binding seat surface 26 defined therebetween. The rotating boot 10 can be mounted or preassembled on a shaft, possibly under tension, via the second binding seat surface 26, e.g. by means of a binding element, in particular a compression ring.
There is a transition region 16 directly adjacent to the first fastening region 12, which in turn is adjacent to a membrane region 18. The membrane region 18 transitions into the second fastening region 14. There is exactly one reinforcement fin 42 in the transition region 16, which is formed circumferentially on an outer surface 17 (see
The membrane part 18 between the first membrane part 32 and the second membrane part 34, which can only be seen in part, shows the design of a rounded part 35, which can also be seen in
An angle α of 5° is formed between the lower surface 43 of the reinforcement fin 42 and an upper surface 33 of the first membrane part 32. The shape of the supporting fin 44 can also be readily seen. This forms a common outer edge 48 without steps, with the first membrane part 32, or the rounded part 35, and an outer surface of the reinforcement fin 42. The supporting fin 16 is located between the upper surface 41 of the reinforcement fin 42 and a lower surface 11 of the excess material 13 of the first fastening region 12. This also has an outer edge 48 aligned with that of the reinforcement fin 42, such that a continuous outer edge 48, i.e. without steps, is obtained in the form of an arc segment.
A height h1 between the upper surface 33 and the first membrane section 32 and the lower surface 43 of the reinforcement fin 42 is lower than a height h2 between the upper surface 41 of the reinforcement fin 42 and the lower surface 11 of the excess material 13. The ratio of the heights h1:h2 is approximately 0.75. The reinforcement fin 42 is closer to the first membrane part 32 of the membrane region 18, such that a height of the supporting fin corresponding to the first height h1 is lower than if the reinforcement fin 42 were displaced toward the first fastening region 12. As a result, the weight can be reduced, and the reinforcement fin 42 is subjected to lower tangential forces than if it were displaced toward the first fastening region 12.
The tendency of the rotating boot 10 to bend in the region of a joint housing outer edge, not shown herein, at high rotational rates is counteracted by the design of the radial fin 46 such that it extends fully under the lower surface 11 of the excess material 13, and the design of the excess material 13 such that a smaller section of the first binding seat region 20 of the first fastening region 12 lies, with a second positioning element 24, in the region of the excess material 13, and thus above the radial fin 46. The excess material 13 has an upper surface 15, which is flush with an upper surface 19 of the first binding seat region 20.
The first fastening region 12 with its first binding seat region 20 and a total of four circumferential fins 50 can be seen, and a material accumulation 52 can be seen on a lower surface 21 of the first fastening region 12, or the first binding seat region 20, which can be placed in a circumferential groove, not shown here, formed accordingly in a joint housing outer part. The second fastening region 14 with the ear-shaped third positioning elements 28 and the wall-shaped bearing or positioning surface 30 forming the fourth positioning element, can also be readily seen in
In
A rotating boot is disclosed that exhibits an improved radial stability, in particular at high rotational rates, such that it can counteract the lubricant pressure resulting from the high centrifugal forces, and also helps to dissipate the centrifugal forces acting on the boot material itself. Ultimately, the rotating boot exhibits an increased service life in comparison with rotating boots known from the prior art, at least at higher rotational rates.
This application is a national stage of, and claims priority to, Patent Cooperation Treaty Application No. PCT/EP2017/054005, filed on Feb. 22, 2017, which application is hereby incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/054005 | 2/22/2017 | WO | 00 |
