pinion bearing unit

Abstract

Pinion bearing unit (10) with - a pinion (20) which is provided with a cylindrical and radially inner seat (21), and - a bearing unit (30) which is housed within the seat (21) and is provided with a radially outer ring (31) which is rigidly connected to the pinion (20) and with a radially inner ring (34), wherein the pinion (20) is provided with an axially inner and radially inner shoulder (40) which axially limits the seat (21) and prevents the pinion (20) from moving axially outwards with respect to the bearing unit (30), and the pinion bearing unit (10) does not provide a ring in the seat (21).

Description

Technical field of the invention

[0001] The present invention relates to a pinion bearing unit. The unit is preferably, but not exclusively, used in motion transmission units for industrial applications. State of the art

[0002] In the industrial sector, pinion bearing units are used, mainly as chain tensioners in units for transmitting motion to drive or working machines.

[0003] The pinion is provided with a radially inner cylindrical seat in which a bearing unit is housed.

[0004] The bearing unit typically comprises a radially inner ring, usually mounted on a central axis of the machine, and a radially outer ring, which is rigidly connected to the pinion. The relative rotation of the outer ring with respect to the inner ring is ensured by several rolling elements, usually balls. The balls are designed to roll within a radially outer raceway formed on the inner ring and a corresponding radially inner raceway formed on the outer ring.

[0005] Due to the stresses that occur during operation of the unit, and in particular due to the oscillating movement exerted by the machine on the pinion, unwanted disassembly of the pinion bearing unit may occur.

[0006] Typically, the loads in this type of application are predominantly radial, as the pinion is used to tension a motion-transmitting chain. However, vibrations caused by the machine can also exert axial loads on the unit. Because the chain is clamped between multiple gears, such axial loads make it difficult to disassemble. Conversely, the sustained effect of vibrations can, over time, lead to disassembly of the pinion relative to the bearing unit: the bearing unit is locked on its central axis, but the pinion can move axially and be disassembled from the bearing unit, causing it to fall off.

[0007] To overcome this disadvantage, two solutions are known that aim to secure the bearing unit and the pinion against each other: - A first solution involves securing the bearing unit with interference in the pinion seat. However, this solution carries the risk of deforming the internal geometry of the bearing unit due to a high interference between the bearing unit and the pinion. Conversely, this solution is not very effective when low interference values ​​are used, so unwanted disassembly of the pinion bearing unit is still possible. - A second solution involves a retaining ring, e.g., a Seeger ring, which can ensure mutual axial locking between the outer ring of the bearing unit and the pinion. However, this second solution also has some disadvantages: - Firstly, it is necessary to construct an axially longer pinion so that there is enough space for inserting the retaining ring; - an additional component must be used; - the presence of an additional component also leads to longer assembly and disassembly times. Summary of the invention

[0008] The object of the present invention is therefore to provide a pinion bearing unit which does not have the disadvantages described above.

[0009] Therefore, within the scope of the present invention, a pinion bearing unit is provided which has the features of the independent claim appended to the present description.

[0010] 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

[0011] The invention will now be described with reference to the accompanying drawings, which show a non-limiting embodiment in which: - Fig. 1 shows a cross section through a pinion bearing unit in a preferred embodiment of the present invention, and - Fig. 2 a detail of the unit in Fig. 1 shows. Detailed description

[0012] According to the Fig. 1, a pinion bearing unit 10 according to the present invention comprises a pinion 20 and a bearing unit 30 and is used on a drive or working machine 100 of the known type and is shown purely schematically.

[0013] The pinion is provided with a radially inner cylindrical seat 21 and with an axially outer and radially inner shoulder 40 that axially delimits the seat 21. The bearing unit 30 is housed inside the seat 21.

[0014] The bearing unit 30 has a central rotation axis X and comprises: - a radially outer ring 31 rigidly connected to the pinion 20, - a radially inner ring 34 rigidly connected to a shaft 110 (of known type and therefore only shown schematically) of the machine 100, - a row 32 of rolling elements 33, in this case balls, inserted between the radial outer ring 31 and the radial inner ring 34, and - at least one sealing device 50 to protect the bearing unit 30 from external contamination.

[0015] 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. Furthermore, the term "axially inward" should be understood as the axial direction toward the machine body to which the pinion bearing unit 10 is mounted. The opposite direction is, of course, referred to as "axially outward."

[0016] According to one embodiment, with reference also to Fig. 2 the pinion 20 is designed so that it can solve the problem of unwanted disassembly from the bearing unit 30, namely to prevent the axial movement of the pinion with respect to the bearing unit 30.

[0017] This is achieved by means of the axially inner shoulder 40, which axially delimits the seat 21 in which the bearing unit 30 is mounted. The shoulder 40 prevents the pinion 20 from moving outward in the axial direction relative to the bearing unit 30, thereby causing it to disassemble and fall off.

[0018] Thanks to this solution, the pinion bearing unit 10 does not require a retaining ring, for example a Seeger ring, which is arranged in the seat 21 to ensure the axial locking between the pinion and the bearing.

[0019] In particular, the shoulder 40 is provided with a free and inner cylindrical surface 41, which lies radially inside a radially outer cylindrical surface 31' of the radially outer ring 31. In this way, an annular bearing surface 42 is formed on the shoulder 40 transverse to the axis X such that it forms an axial bearing surface for the radially outer ring 31.

[0020] Advantageously, the shoulder 40 of the pinion has the minimum axial width L sufficient to support the axial loads, for example, a width between 2.4 mm and 2.6 mm. This smaller axial width limits as much as possible the increase in the axial dimensions of the pinion 20 due to the presence of the shoulder 40. In any case, the axial width of the pinion 20 is still smaller than the axial width required by the pinion when using the Seeger ring according to the prior art to ensure axial locking between the bearing unit and the pinion. Indeed, the Seeger ring solution requires both the axial dimensions for the ring seat and the axial dimensions to ensure a shoulder downstream of the Seeger ring, which is necessary to withstand the axial loads.Furthermore, since the seat for the Seeger ring represents a structural weakening of the pinion, the state-of-the-art solution requires a further increase in the axial dimension of the pinion to compensate for the corresponding reduction in material due to the creation of the seat for the Seeger ring.

[0021] However, in the axially inward direction, there is no possibility of the pinion falling, as it would be stopped by the frame of the machine 100. In any case, it is advantageous to avoid contact between the pinion 20 and the frame of the machine 100, and in particular to prevent mutual axial movement between the pinion and the radial outer ring of the bearing unit, in order to avoid the occurrence of wear phenomena between the contacting surfaces.

[0022] It is therefore advantageous to provide a slight interference between the seat 21 of the pinion 20 and the radially outer cylindrical surface 31' of the radially outer ring 31 of the bearing unit. However, the interference value to be adopted may be lower than the interference value required according to the prior art for the mutual locking of the bearing unit and the pinion in the absence of a mechanical stop (the shoulder): While the prior art requires the use of tolerance class M7, according to the invention it is sufficient to adopt tolerance class N7, which provides lower interference values ​​than the previous class. Considering a bearing unit with an outer diameter of 40 mm for a typical application, this results in a change from an interference between 0.08 mm and 0.33 mm (tolerance class M7) to an interference between 0 and 0.25 mm (tolerance class N7).By using smaller interference values, the risk of deformation of the internal geometry of the bearing is avoided and the radially outer ring can be correctly fixed near the shoulder 40 on its annular surface 42.

[0023] In order to avoid axial movements of the pinion bearing unit 10 as a whole, the bearing unit 30 can advantageously be axially fixed by a retaining ring 60, e.g. a Seeger ring, or a locking pin in order to secure the radial inner ring 34 on the shaft 110 of the machine 100.

[0024] From a production process perspective, the solution according to the present invention requires no additional steps compared to the known embodiments. According to the prior art, precision machining is still required to manufacture the bearing unit's seat in the pinion, whether using an interference fit between the pinion and the outer ring or using a Seeger ring. The present solution also requires the same operation, but no additional machining.

[0025] In summary, according to the present invention, the solution regarding the pinion bearing unit makes it possible to have no mutual axial movements between the bearing unit and the pinion and thus to avoid accidental disassembly.

[0026] In addition to the embodiment of the invention described above, there are, of course, numerous other variants. It should also be understood that these embodiments are merely exemplary and do not limit the scope of the invention, its applications, or its possible interpretations. On the contrary, although the above description enables those skilled in the art to implement the present invention according to at least one exemplary embodiment thereof, it should be understood that numerous variations of the described components are possible without thereby departing from the scope of the invention as defined in the appended claims, interpreted literally and / or according to their legal equivalents.

Claims

[1] Pinion bearing unit (10) comprising - a pinion (20) provided with a cylindrical and radially inner seat (21), and - a bearing unit (30) housed within the seat (21) and provided with a radially outer ring (31) integrally connected to the pinion (20) and with a radially inner ring (34), the pinion bearing unit (10) characterized by is that in combination - the pinion (20) is provided with an axially inner and radially inner shoulder (40) which axially delimits the seat (21) and prevents the pinion (20) from moving axially outwards with respect to the bearing unit (30), and - the pinion bearing unit (10) does not have a retaining ring in the seat (21). [2] Unit (10) according to claim 1, wherein there is an interference between the seat (21) of the pinion (20) and a cylindrical surface (31') located radially outward of the radially outer ring (31), which interference is included in the tolerance class N7. [3] Unit (10) according to claim 2, wherein the interference is between 0 mm and 0.25 mm. [4] Unit (10) according to one of the preceding claims, wherein the shoulder (40) of the pinion (20) is provided with an annular bearing surface (42) transverse to the axis (X) to define an axial bearing for the radially outer ring (31). [5] Unit (10) according to claim 4, wherein the shoulder (40) of the pinion (20) has an axial width (L) which is between 2.4 mm and 2.6 mm.

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