Storage unit with retaining cage

Abstract

Bearing unit (30) with a central axis of rotation (X) and a retaining cage (40) for a plurality of rolling elements (34) inserted between a radial outer ring (31) and a radial inner ring (33), the retaining cage (40) being provided with several movable sections (50) made of polymeric material, identical to one another and arranged side by side in the circumferential direction, and each movable section (50) having at its ends a first engagement section (51) and a second engagement section (52) configured to define a dovetail connection between the first engagement section (51) of a first movable section (50') and the second engagement section (52) of a second movable section (50"), which is circumferentially adjacent to the first movable section (50') to provide circumferential and radial restraint as well as an axial degree of freedom between the two movable sections (50', 50") to create.

Description

Technical field of the invention

[0001] The present invention relates to a bearing unit with a retaining cage. State of the art

[0002] Known bearing units with a retaining cage include: - a radially outer ring, - a radially inner ring, - several rolling elements, in particular balls, inserted between the two rings, the inner ring and the outer ring, to allow their relative rotation, and - a retaining cage which holds the balls in the respective circumferential positions and in turn comprises a circular base frame and a plurality of pins which are integral with the frame, spaced apart in the circumferential direction and which, in pairs, define a plurality of cavities for receiving the respective balls.

[0003] The base frame is a continuous structural element that extends circumferentially, forming a solid base and providing the cage as a whole with the necessary rigidity to keep the balls evenly spaced. The studs, however, that contain and hold the balls together, must exhibit essentially elastic behavior, allowing them to spread apart to allow the balls to be inserted and then essentially close around the balls to hold them in their respective cavities.

[0004] These retaining cages are typically used in high-speed, high-vibration bearing units used in both the automotive sector, e.g., in powertrains, and the industrial sector, e.g., in machine tool spindles, and are typically manufactured by injection molding a polymer material, also to compensate for poor lubricants.

[0005] If a bearing unit with a retaining cage, such as that known from the known design described above, is used in an application in which high axial loads or misalignments occur between the shaft and the bearing unit, the retaining cage can be significantly deformed during the relative rotation between the rings of the bearing unit, so that the journals are no longer able to hold the balls in the cavities, which leads to an absolutely undesirable disassembly of the bearing unit. Summary of the invention

[0006] An object of the present invention is to provide a bearing unit with a retaining cage which does not have the disadvantage described above.

[0007] Accordingly, the present invention describes a bearing unit with a retaining cage having movable sections, which comprises the features of the independent claim appended to the present description.

[0008] Further preferred and / or particularly advantageous embodiments of the invention are described according to the features in the appended dependent claims. Short description of the drawings

[0009] The invention will now be described with reference to the accompanying drawings which show non-limiting embodiments thereof, in which: - Fig. 1 is a partial cross-section of a first preferred embodiment of a bearing unit according to the present invention, - Fig. 2 an axonometric view of the retaining cage of the bearing unit in Fig. 1 is, - Fig. 3 an axonometric partial view of the underside of the retaining cage in Fig. 2 is, - Fig. 4 an enlarged axonometric view of the underside of a movable section of the cage in Fig. 2 is, - Fig. 5 an enlarged axonometric side view of a movable section in Fig. 4 is, and - Fig. 6 another enlarged axonometric side view of a movable section in Fig. 4 is. Detailed description

[0010] In Fig. 1, reference numeral 30 denotes a bearing unit as a whole according to a preferred embodiment of the present invention.

[0011] The bearing unit 30 has a central rotation axis X and comprises: - a radially outer ring 31, which is preferably, but not necessarily, stationary, - a radially inner ring 33, which is preferably, but not necessarily, rotatable, - a row 32 of rolling elements 34 inserted between the radial outer ring 31 and the radial inner ring 33, and - a cage 40 for holding the rolling elements 34 of the row 32 of rolling elements in position.

[0012] In this description and the claims, terms and expressions indicating positions and orientations, such as "radial" and "axial," are to be understood with reference to the central rotational axis X of the bearing unit 30, unless otherwise stated. For simplicity, the term "ball" may be used in this description and the accompanying drawings instead of the more general term "rolling element," and the same reference numerals are used.

[0013] With reference to Fig. 2, the cage 40 according to the present invention comprises a plurality of movable sections 50 made of polymeric material, identical to one another, and arranged circumferentially side by side. Each movable section has a first engagement section 51 and a second engagement section 52 at its ends. The two engagement sections are shaped to form a dovetail joint, so that the first engagement section 51 of a first movable section 50' can be connected to a second engagement section 52 of a second movable section 50", which is circumferentially adjacent to the first movable section 50', to form a circumferential and radial connection between the two movable sections 50', 50". The same connection is reproduced for each pair of adjacent movable sections, so that a single cage 40, such as the one shown in Fig. 2, is made of polymer material in which all movable sections 50 are circumferentially and radially connected to one another.

[0014] Each movable section 50 also has: - a base rib 41 formed by a flattened annular element extending around the axis X, - a pair of pins 42, which are circumferentially spaced from each other and have a curved shape. The two pins 42 each have concave surfaces 42' that face each other, - a cavity 43 for receiving a respective ball 34. The cavity 43 is limited by the two pins 42.

[0015] If all movable sections 50 are circumferentially connected, the cage 40 then has: - a base frame 44 extending over 360° and formed by the base rib 41 of each movable section 50, - several pairs of pins 42, each pair of pins belonging to a movable section 50, and - a plurality of cavities 43, each cavity being defined by a corresponding pair of pins 42 which receive all the corresponding balls 34 of the ball row 32.

[0016] As previously mentioned, the dovetail connection between the two engaging portions 51, 53 of two circumferentially adjacent movable portions 50', 50" defines a circumferential and radial constraint between the two adjacent movable portions. However, this connection provides the two adjacent portions with a degree of freedom (within certain limits, as explained below) in the axial direction, allowing the movable portions to slide axially relative to each other in response to different axial loads and / or misalignments to which they may be subjected during operation.

[0017] A cage 40 with axially independent movable sections 50, as in the present invention, offers a notable advantage in applications involving misalignments of the shaft on which the bearing unit is mounted, or with high axial loads that are not evenly distributed in the circumferential direction. This cage allows a single movable section to move axially to accommodate the movement caused by the misalignment and / or the axial load, while the other movable sections remain in position. This prevents deformation of the cage 40 and eliminates the risk of the balls falling out of their respective cavities.

[0018] Advantageously, the movable portion 50 subjected to these influences can return to its original position when the effect of the misalignment and / or axial load is no longer present. With reference to Fig. 3, the cage 40 may include an annular elastic metal element 60 (e.g., an annular metal spring) that helps to hold the movable portions in position and assists the movable portion in returning to its position after axial movement.

[0019] With reference to Fig. 4, the annular elastic element 60 extends circumferentially within a seat 53 formed in the base rib 41 of each movable portion 50.

[0020] With reference to the Fig. 5 and Fig.6, the first engagement portion 51 of the dovetail joint between two adjacent movable portions comprises two shaped posts 51' radially opposed to each other and defining an end space 54 and a gap 54', the gap 54' having a radial width greater than the radial width of the end space 54.

[0021] On the other hand, the second engagement portion 52 of the dovetail joint comprises an end edge 55 and an intermediate core 55', wherein the end edge 55 has a radial width that is greater than the radial width of the intermediate core 55'.

[0022] The radial width of the end edge 55 of the second engagement portion 52 of the dovetail joint is almost identical to the radial width of the intermediate space 54' of the first engagement portion 51, except for a small radial clearance. Likewise, the radial width of the intermediate core 55' of the second engagement portion 52 is almost identical to the radial width of the end space 54 of the first engagement portion 51, but with a small radial clearance.

[0023] The dovetail joint is made by snapping: - the end edge 55 of the second engagement portion 52 into the space 54' of the first engagement portion 51, and - the intermediate core 55' of the second engagement portion 52 into the end space 54 of the first engagement portion 51.

[0024] This means that two adjacent sections are circumferentially connected to each other, since the end edge 55 of the movable section cannot come out of the end space 54, which has a smaller radial width.

[0025] On the other hand, as already mentioned, adjacent movable sections 50', 50" have mutual freedom of movement. However, this movement should be limited, which is achieved by forming a stop in the axial direction between a first stop surface 56 of the first engagement section 51 and a second stop surface 57 of the second engagement section 52. This avoids the risk of a movable section becoming detached from the remaining "package" of movable sections forming the cage, despite the presence of the annular elastic element 60.

[0026] Advantageously, a radially inner surface 58 of the second engagement portion 52 may be dimensioned to accommodate all radial loads transferred between the first and second portions.

[0027] In short, a bearing unit provided with a polymeric retaining cage circumferentially interconnecting a plurality of axially movable sections according to the present invention substantially reduces the risk of the bearing unit becoming disengaged from the polymeric cage when the bearing unit is subjected to a high axial load or when there is a misalignment between the shaft and the bearing unit.

[0028] Furthermore, the disclosed solution does not require a change in the method for assembling the cage in the bearing unit, and it does not change the dimensions of the cage frame compared to the dimensions of a standard polymer cage.

[0029] On the other hand, the present solution has the additional advantage of allowing the replacement of individual worn movable sections instead of the entire cage.

[0030] Finally, the axial movement of the movable section of the cage is kept under control by simple mechanical end stop means, and the annular elastic element helps each individual section affected by the axial movement to return to its original position.

[0031] In addition to the embodiments of the invention described above, numerous other variations exist. These embodiments are provided merely as examples and do not limit the scope of the invention, its applications, or its possible embodiments. While the description provided above enables one skilled in the art to practice the present invention according to at least one exemplary embodiment, numerous variations of the described components could be used without departing from the scope of the invention as defined in the appended claims, which are to be interpreted literally and / or in accordance with their legal equivalents.

Claims

[1] Bearing unit (30) having a central axis of rotation (X) and comprising: - a radially outer ring (31), - a radially inner ring (33), - a row (32) of rolling elements (34) arranged between the radial outer ring (31) and the radial inner ring (33), and - a retaining cage (40) for holding the rolling elements, the bearing unit (30) characterized byis that the cage (40) comprises a plurality of movable sections (50) which are identical to one another, arranged circumferentially adjacent to one another around the central axis of rotation (X), and each having a respective first (51) and a respective second (52) engagement section for their own arrangement with a relative second (52) and a relative first (51) engagement section of the two circumferentially adjacent movable sections (50), wherein each first (51) and each second (52) engagement section of each movable section (50) forms a respective circumferential boundary, a respective radial boundary, and a respective axial degree of freedom with each second (52) and each first (51) engagement section of circumferentially adjacent movable sections (50). [2] A bearing unit (30) according to claim 1, wherein each movable section 50 comprises - a base rib (41) defined by a flattened annular element extending around the axis (X), - a pair of pins (42) which are circumferentially spaced from each other and have an arcuate shape, and - a recess (43) defined by the pair of pins (42) for holding a respective rolling element (34). [3] Bearing unit (30) according to claim 1 or 2, wherein the cage (40) comprises an annular elastic member (60) made of metal for holding the plurality of movable sections (50) in position and for restoring the axial position of each movable section (50) upon axial movement. [4] Bearing unit (30) according to claim 3, wherein the annular elastic element (60) extends circumferentially within a seat (53) obtained in each movable portion (50) in correspondence with the base rib (41). [5] Bearing unit (30) according to one of the preceding claims, wherein the first engagement portion (51) comprises two shaped posts (51') radially opposed to each other and defining an end space (54) and a gap (54'), the gap (54') having a radial width greater than the radial width of the end space (54). [6] Bearing unit (30) according to one of the preceding claims, wherein the second engagement portion (52) comprises an end edge (55) and an intermediate core (55'), the end edge (55) having a radial width that is greater than the radial width of the intermediate core (55'). [7] Bearing unit (30) according to claims 5 and 6, wherein the radial width of the end edge (55) of the second engagement portion (52) is almost equal to that of the intermediate space (54') of the first engagement portion (51) and the radial width of the intermediate core (55') of the second engagement portion (52) is almost equal to that of the end space (54) of the first engagement portion (51). [8] Bearing unit (30) according to one of the preceding claims, wherein the engagement portions (51, 52) define a stop in the axial direction between a first stop surface (56) of the first engagement portion (51) and a second stop surface (57) of the second engagement portion (52). [9] Bearing unit (30) according to one of the preceding claims, wherein the second engagement portion (52) has a radially inner surface (58) for receiving radial loads transmitted between the first engagement portion (51) of a first movable portion (50') and the second engagement portion (52) of a second movable portion (50") circumferentially adjacent to the first movable portion (50').

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