Pinion bearing unit

Abstract

The pinion bearing unit (10) has: a pinion (20) provided with a cylindrical and radially inner seat (21); and-a bearing unit (30) housed in said seat (21) and provided with a radially outer ring (31) rigidly connected to said pinion (20), and with a radially inner ring (34), said radially outer ring (31) being provided with an axially inner and radially inner shoulder (40), said radially outer ring (31) being rigidly connected to said pinion (20), the shoulder (40) delimits the seat (21) in the axial direction and prevents the pinion (20) from moving outwards in the axial direction relative to the bearing unit (30), and the pinion bearing unit (10) does not have a retaining ring in the seat (21).

Description

Technical Field

[0001] The present invention relates to a pinion bearing unit which is preferably, but not exclusively, used in a motion transmission unit for industrial applications. Background Art

[0002] In industrial applications, pinion bearing units are primarily used as chain tensioners in units for transmitting motion for driving or operating ( / working / running) machines.

[0003] The pinion is provided with a radially internal cylindrical seat in which the bearing unit is accommodated.

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

[0005] Due to stresses occurring during operation of the unit, and in particular due to vibrating movements caused by the machine on the pinion, undesired demounting of the pinion bearing unit may occur.

[0006] Typically, in this type of application, the loads are predominantly radial, since the pinion serves to tension the motion transmission chain. However, vibrations caused by the machine may also determine axial loads on the unit. The chain is locked between several gears and is therefore difficult to disengage with such axial loads. In contrast, the prolonged effects of vibrations over time may lead to disengagement of the pinion relative to the bearing unit: the bearing unit is locked on the center axis, but the pinion may move in the axial direction and disengage from the bearing unit, thus falling down.

[0007] In order to overcome this disadvantage, two solutions are known which aim to fix the bearing unit and the pinion to each other:

[0008] - A first solution provides for the bearing unit to be mounted in the seat of the pinion in an interference manner. However, this solution carries the risk that high interference values ​​between the bearing unit and the pinion may lead to deformation of the internal geometry of the bearing unit. On the contrary, this solution is not very effective when using low interference values, so that undesired disassembly of the pinion bearing unit may still occur.

[0009] - A second solution provides for the use of a retaining ring (eg a Seeger ring) which can ensure a mutual axial locking between the outer ring of the bearing unit and the pinion. However, this second solution also has some disadvantages:

[0010] - First, the pinion must be designed to be axially longer to have enough space for inserting the retaining ring;

[0011] - Additional components are required;

[0012] - The presence of additional components also requires longer installation and removal times. Summary of the invention

[0013] The present invention therefore aims to provide a pinion bearing unit which does not have the above-mentioned disadvantages.

[0014] The invention therefore provides a pinion bearing unit having the features set out in the independent claim appended to the present description.

[0015] Preferred and / or particularly advantageous further embodiments of the invention are described according to the features stated in the attached dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will now be described with reference to the accompanying drawings showing non-limiting example embodiments of the invention, in which:

[0017] - Figure 1 shows a cross section of a pinion bearing unit in a preferred embodiment of the invention, and

[0018] - Figure 2 Shows Figure 1 Details of the units in . DETAILED DESCRIPTION

[0019] Reference Figure 1 , a pinion bearing unit 10 according to the present invention comprises a pinion 20 and a bearing unit 30, and is applied to a driving or operating machine 100 of a known type and is only schematically shown.

[0020] The pinion is provided with a radially internal cylindrical seat 21 and with an axially outer and radially inner shoulder 40 which axially delimits the seat 21. A bearing unit 30 is accommodated in the seat 21.

[0021] The bearing unit 30 has a central axis of rotation X and comprises:

[0022] - a radial outer ring 31 rigidly connected to the pinion 20;

[0023] a radially inner ring 34 rigidly connected to a shaft 110 of the machine 100 (of a known type and therefore only shown schematically);

[0024] a row 32 of rolling bodies 33 , in the present case balls, between the radially outer ring 31 and the radially inner ring 34 ; and

[0025] - At least one sealing device 50 to protect the bearing unit 30 from external contaminants.

[0026] Throughout the present specification and claims, terms and expressions indicating positions and orientations (such as "radial" and "axial") should be understood with reference to the central rotation axis X of the bearing unit 30. Furthermore, the term "axially internal" should be understood as the axial direction towards the body of the machine to which the pinion bearing unit 10 is applied. The opposite direction will obviously be indicated by the term "axially external".

[0027] Therefore, according to one design, also referring to Figure 2 The pinion 20 is produced in such a way that the problem of (the pinion 20) being undesirably removed from the bearing unit 30 can be solved, that is, the axial movement ( / movement) of the pinion relative to the bearing unit 30 can be prevented.

[0028] This is achieved by an axially inner shoulder 40 which axially delimits the seat 21 in which the bearing unit 30 is mounted. In fact, the shoulder 40 prevents the pinion 20 from being able to move in the axially outward direction relative to the bearing unit 30 and thus become demounted and fall off.

[0029] This solution means that the pinion bearing unit 10 does not require a retaining ring (eg a Seeger ring) arranged in the seat 21 to ensure axial locking between the pinion and the bearing.

[0030] More specifically, the shoulder 40 is provided with a free cylindrical inner surface 41, which is located radially inside the cylindrical radial outer surface 31' of the radial outer ring 31. In this way, an annular abutment surface ( / abutment surface / adjacent surface) (abutment surface) 42 is formed on the shoulder 40 transverse to the axis X, so that an axial abutment portion of the radial outer ring 31 is formed.

[0031] Advantageously, the shoulder 40 of the pinion has a minimum axial width L sufficient to support the axial load, for example a width between 2.4 mm and 2.6 mm. This reduced 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 of the pinion that would be required to use a sig ring according to the prior art to ensure the axial locking between the bearing unit and the pinion. In fact, the solution of the sig ring requires both the axial dimensions of the seat for the ring necessary to withstand the axial load and the axial dimensions for ensuring the shoulder (downstream of the sig ring). In addition, since the seat for the sig ring constitutes a structural weakening of the pinion, it is necessary according to the solution of the prior art to further increase the axial dimensions of the pinion to compensate for the corresponding reduction in material caused by the creation of the sig ring seat.

[0032] However, in the axially inward direction, the pinion cannot fall off, since it will be stopped by the frame of the machine 100. In any case, it is preferable 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 prevent wear phenomena from occurring between the contact surfaces.

[0033] Advantageously, it is therefore expedient to provide a slight interference between the seat 21 of the pinion 20 and the cylindrical radial outer surface 31 ' of the radial outer ring 31 of the bearing unit. However, the interference value to be adopted can be lower than the interference value required to fix the bearing unit and the pinion to each other without a mechanical stop (shoulder) according to the prior art: in fact, although it is necessary to use the M7 tolerance grade according to the prior art, it is sufficient according to the invention to adopt the N7 tolerance grade providing a lower interference value than the previous grade. For typical applications, considering that the bearing unit has an outer diameter of 40 mm, there is a variation between an interference of between 0.08 mm and 0.33 mm (M7 tolerance grade) and an interference of between 0 mm and 0.25 mm (N7 tolerance grade). The use of a smaller interference value avoids any risk of deformation of the internal geometry of the bearing and also allows the radial outer ring to be correctly mounted against its annular surface 42 near the shoulder 40.

[0034] Advantageously, to prevent axial movement of the pinion bearing unit 10 as a whole, the bearing unit 30 can be locked axially such that the radial inner ring 34 is fixed to the shaft 110 of the machine 100 by a retaining ring 60 (eg a siger ring) or a locking pin.

[0035] From the point of view of the production process, the solution according to the invention does not require additional steps relative to those required by the known embodiments. In fact, according to the prior art operation, the production of the seat of the bearing unit in the pinion, using both the interference fit between the pinion and the outer ring and the sig ring, still requires the performance of precise machining. The present solution also requires the same operation without any additional processing.

[0036] In summary, the concept according to the invention with regard to the pinion bearing unit makes it possible to prevent mutual axial movements between the bearing unit and the pinion and thus avoids unintentional unmounting.

[0037] In addition to the embodiments of the present invention as described above, it should be understood that many other variations exist. It should also be understood that these embodiments are exemplary only and do not limit the scope of the present invention, its application or its feasible configuration. In contrast, although the above description enables those skilled in the art to implement the present invention according to at least one exemplary embodiment of the present invention, it should be understood that many variations of the described components are feasible, and will not therefore depart from the scope of the present invention as defined in the appended claims as interpreted literally ( / text) and / or interpreted according to its legal equivalents.

Claims

1. A pinion bearing unit (10), include: - a pinion (20) provided with a cylindrical and radially inner seat (21); as well as a bearing unit (30) housed in the seat (21) and provided with a radially outer ring (31) and a radially inner ring (34), the radially outer ring (31) being integrally connected to the pinion (20), The pinion bearing unit (10) is characterized by the following combination: - the pinion (20) is provided with an axially inner and radially inner shoulder (40) which delimits the seat (21) in the axial direction and prevents the pinion (20) from moving outwardly in the axial direction relative to the bearing unit (30), and The pinion bearing unit (10) has no retaining ring in the seat (21).

2. The pinion bearing unit (10) according to claim 1, It is characterized in that There is an interference between the seat (21) of the pinion (20) and the cylindrical radially outer surface (31') of the radially outer ring (31), said interference being included in the tolerance class N7.

3. The pinion bearing unit (10) according to claim 2, It is characterized in that The interference is between 0 mm and 0.25 mm.

4. A pinion bearing unit (10) according to any one of the preceding claims, It is characterized in that The shoulder (40) of the pinion (20) is provided with an annular abutment surface (42) transverse to the axis (X) and so as to define an axial abutment for the radially outer ring (31).

5. The pinion bearing unit (10) according to claim 4, It is characterized in that The axial width (L) of the shoulder (40) of the pinion (20) is in the range between 2.4 mm and 2.6 mm.

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