Pinion bearing unit

Abstract

A pinion bearing unit (10) has a pinion (20) and a bearing unit (30), the pinion (20) being provided with a cylindrical and radially inner seat (21), the bearing unit (30) being housed within the seat (21); the pinion gear (20) has at least one pair of fins (40, 40 '), each of which is arranged on a respective outer annular wall (22, 22') of the pinion gear (20) and extends in the axial direction on opposite sides of the seat (21) to deflect by 90 DEG so as to abut the bearing unit (30) such that the bearing unit (30) is locked in the axial direction within the seat (21).

Description

Technical Field

[0001] The present invention relates to a pinion bearing unit, preferably but not exclusively for use in a motion transmission unit for industrial machinery, and the following description will make particular reference to this pinion bearing unit without thereby losing its general character. Background Art

[0002] In industrial machinery, a pinion bearing unit of a known type is mainly used as a chain tensioner in a motion transmission unit and comprises:

[0003] - a pinion provided with a radially internal cylindrical seat; and

[0004] - A bearing unit housed in the cylindrical seat.

[0005] The bearing unit usually comprises: a radial inner ring, usually mounted on the central axis of the motion transmission unit; and a radial outer ring, rigidly connected to the pinion (opinion). 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 on the inner side of the radial outer raceway formed on the inner ring and on the inner side of the corresponding radial inner raceway formed on the outer ring.

[0006] Due to stresses occurring during operation of the unit, and in particular due to vibrating movements caused by the motion transmission unit on the pinion, an undesired demounting of the pinion bearing unit may occur.

[0007] Typically, in this type of application, the load(s) are predominantly radial, since the pinion serves to tension the motion transmission chain. However, the vibrations caused by the motion transmission unit 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 and therefore fall out.

[0008] In order to overcome this disadvantage, two solutions are known which aim to fix the bearing unit and the pinion to each other:

[0009] - 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.

[0010] - 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:

[0011] - First, the pinion must be designed to be axially longer to have enough space for inserting the retaining ring;

[0012] - Additional components are required;

[0013] - The presence of additional components also requires longer installation and removal times. Summary of the invention

[0014] The present invention therefore aims to provide a pinion bearing unit which does not have the above-mentioned disadvantages.

[0015] The invention therefore provides a pinion bearing unit having the features set out in the independent claim appended to the present description.

[0016] 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

[0017] The invention will now be described with reference to the accompanying drawings showing non-limiting example embodiments of the invention, in which:

[0018] - Figure 1 shows a cross section of a pinion bearing unit in a preferred embodiment of the present invention and according to an intermediate mounting configuration,

[0019] - Figure 2 Shows Figure 1 Axonometric drawing of the unit in

[0020] - Figure 3 Shown in cross section and on an enlarged scale Figure 1 Details of the units in

[0021] - Figure 4 Shown in cross section in final installed configuration Figure 1 , and some components are removed for clarity. DETAILED DESCRIPTION

[0022] Reference Figure 1 and Figure 2 , 10 shows a pinion bearing unit 10 as a whole, which is applied to a motion transmission unit 100 of a known type and which is only schematically shown.

[0023] The pinion bearing unit 10 has a central rotation axis X and comprises:

[0024] - a bearing unit 30; and

[0025] - a pinion 20 provided with a radially internal cylindrical seat 21 for accommodating a bearing unit 30, and provided with at least one pair of fins 40 and 40', at least one pair of fins 40 and 40' being arranged on respective lateral annular walls 22 and 22' of the pinion 20.

[0026] The first fin 40 of the pair of fins 40, 40' extends axially toward the outside (i.e., away from the motion transmission unit 100), and the second fin 40' of the pair of fins 40, 40' extends axially toward the inside (i.e., toward the motion transmission unit 100). The geometry and function of the fins 40, 40' will be described in more detail below.

[0027] The bearing unit 30 comprises, for its part:

[0028] - a radial outer ring 31 rigidly connected to the pinion 20;

[0029] a radially inner ring 34 rigidly connected to the shaft 110 of the motion transmission unit 100 (of a known type and therefore only shown schematically);

[0030] a row 32 of rolling elements 33 (in this case balls) between a radially outer ring 31 and a radially inner ring 34; and

[0031] At least one sealing device 50 arranged between the radially inner ring 34 and the radially outer ring 31 to protect the bearing unit 30 from external contaminants.

[0032] Throughout the present specification and claims, terms and expressions indicating position and orientation, 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. Obviously, the opposite direction will be indicated by the term "axially external".

[0033] According to one design, the pinion 20 is produced in such a way that the problem of undesired demounting (of the pinion 20 ) from the bearing unit 30 can be solved, i.e., axial movement ( / disassembly) of the pinion relative to the bearing unit 30 is prevented.

[0034] The main objectives of the program are to:

[0035] - improving the mounting of the pinion bearing unit, thereby reducing the interference connection between the radial outer ring of the bearing unit; and

[0036] - Axially locks the bearing unit around the entire circumference.

[0037] This is achieved by means of fins 40 , 40 ′ with which the pinion 20 is provided.

[0038] Each fin 40, 40' comprises:

[0039] a prismatic base 41 fastened to the annular wall 22 , 22 ′ of the pinion; and

[0040] - Teeth 42 , orthogonal to the prismatic base 41 , from which they project in the axial direction.

[0041] Also refer to Figure 4 Once the bearing unit 30 is mounted in the seat 21 of the pinion gear, the teeth 42 of the fins 40, 40' are deflected, i.e. folded by about 90°, to abut the bearing unit 30. In particular, the abutment is achieved using the outer annular edge 310, 310' of the radial outer ring 31 as an abutment element. Thus, the teeth 42 of the fins 40, 40' are transformed from a configuration having an axial extent before mounting the bearing unit to a configuration having a substantially radial extent after mounting the bearing unit 30 in the seat 21 of the pinion gear 20.

[0042] In this way, the fins 40 , 40 ′ folded at 90° engage with the corresponding annular edges 310 , 310 ′ of the radial outer ring 31 , locking the entire bearing unit 30 axially in the seat 21 of the pinion 20 .

[0043] Advantageously, the teeth 42 of the fins 40, 40' have a cross section S with a thickness ranging between 1.5 mm and 2.0 mm. A cross section with a thin thickness allows the teeth 42 of the fins 40, 40' to be very easily folded using a hammer or compression tools. Values ​​less than 1.5 mm may cause the teeth of the fin to break, while values ​​greater than 2.0 mm will make the folding of the teeth difficult.

[0044] Advantageously, in order to be able to ensure axial locking of the bearing unit around the entire circumference of the annular edge 310, 310', there may be more than one fin 40, 40' for each annular wall 22, 22' of the pinion 20. A feasible solution deduced by calculations and experimental tests provides that on each annular wall 22, 22', eight corresponding fins 40, 40' are arranged equidistant from one another in the circumferential direction. This number of fins represents the best solution for two conflicting requirements: ensuring a secure hold of the bearing unit and not complicating the process of folding the fins.

[0045] Advantageously, the expedient is 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 according to the prior art it is necessary to use the M7 tolerance grade, according to the invention it is sufficient to adopt the N7 tolerance grade providing a lower interference value than the previous grade. For a typical application, 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.

[0046] Advantageously, to prevent axial movement of the pinion bearing unit 10 as a whole, the bearing unit 30 can be locked axially to fix the radial inner ring 34 to the shaft 110 of the motion transmission unit 100 by means of a retaining ring 60 (eg a Seeger ring) or a locking pin.

[0047] In summary, the process of installing the bearing unit 30 in the seat 21 of the pinion 20 is very simple and includes the following two steps:

[0048] - inserting the bearing unit 30 into the seat 21 of the pinion so that the coupling between the seat 21 and the radial outer ring 31 can be achieved with a slight interference according to the N7 tolerance class; and

[0049] The teeth 42 of the fins 40 , 40 ′ are folded approximately to 90° by means of a hammer or a compression tool so that they come to rest at corresponding abutments formed by the annular edge 310 , 310 ′ of the radially outer ring 31 of the bearing unit 30 .

[0050] Therefore, from the point of view of the production process, the solution according to the invention is simpler than the known embodiments. In fact, according to the operation of the prior art, the production of the seat of the bearing unit in the pinion, both using a significant interference between the pinion and the outer ring and using a sig ring, still requires the performance of precise machining. However, the present solution only requires a simpler operation of folding the fins to ensure the axial locking of the bearing unit.

[0051] In summary, the solution according to the invention with respect to the pinion bearing unit achieves the intended objects, since it makes it impossible for mutual axial movements between the bearing unit and the pinion and thus avoids unintentional demounting.

[0052] 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), comprising a pinion (20) and a bearing unit (30), wherein the pinion (20) is provided with a cylindrical and radially inner seat (21), the bearing unit (30) is accommodated in the seat (21) and is provided with a radial outer ring (31) and a radial inner ring (34), the radial outer ring (31) being connected to the pinion (20), the pinion bearing unit (10) being characterized in that the pinion (20) is provided with at least one pair of fins (40, 40'), wherein: The fins (40, 40') are arranged on the corresponding axially outer annular walls (22, 22') of the pinion (20) and extend axially on opposite sides of the seat (21) so as to deflect when the pinion bearing unit (10) is assembled, thereby abutting against the bearing unit (30), so that the bearing unit (30) is locked in the seat (21) in the axial direction.

2. The pinion bearing unit (10) according to claim 1, characterized in that: The fins (40, 40') of the at least one pair of fins abut against the outer annular edge (310, 310') of the radial outer ring (31) of the bearing unit (30).

3. The pinion bearing unit (10) according to claim 1 or 2, characterized in that: Each fin (40, 40') comprises: - a prismatic base (41) firmly fixed to the annular wall (22, 22') of said pinion (20); and - teeth (42) orthogonal to said prismatic base (41), said teeth (42) protruding axially from said prismatic base (41).

4. The pinion bearing unit (10) according to claim 3, characterized in that The teeth (42) of the fins (40, 40') have a cross section (S) with a thickness ranging between 1.5 mm and 2.0 mm.

5. The pinion bearing unit (10) according to any one of the preceding claims, characterized in that For each annular wall (22, 22') of the pinion (20), there are eight fins (40, 40').

6. A pinion bearing unit (10) according to any one of the preceding claims, characterised 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.

7. The pinion bearing unit (10) according to claim 6, characterized in that The interference is between 0 mm and 0.25 mm.

8. A method for assembling a pinion bearing unit (10) according to any one of the preceding claims, wherein: The pinion bearing unit comprises: - a pinion (20) provided with a cylindrical and radially inner seat (21) and provided with at least one pair of fins (40, 40'), each fin of the at least one pair of fins (40, 40') being arranged on a respective outer annular wall (22, 22') of the pinion (20); and - a bearing unit (30) housed in the seat (21) and provided with a radial outer ring (31) rigidly connected to the pinion (20), The method comprises the following steps: a) inserting the bearing unit (30) into the seat (21) of the pinion (20); and b) deflecting the teeth (42) of the fins (40, 40') by approximately 90° so that the teeth (42) come to rest at corresponding abutments formed by an annular edge (310, 310') of the radial outer ring (31) of the bearing unit (30).

9. The assembly method according to claim 8, characterized in that: Step a) is performed by performing the coupling between the seat (21) and the radially outer ring (31) with an interference according to tolerance class N7.

10. The assembly method according to claim 8 or 9, characterized in that: Step b) is performed by means of a hammer or a compression tool.

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