Tensioner for a belt drive

Abstract

Tensioner (1) for a belt drive comprising a base (2) securable to a support structure (3), an arm (4) constrained to the base (2) and movable relative thereto, a pulley (5) carried by the arm (4) and rotatable relative thereto about its own axis (B), and a spring (9) acting on the arm (4) to push the pulley (5) into contact with the belt, wherein the pulley (5) is mounted on the arm by means of a pivot (10) coaxial thereto and at least one bearing (12, 13); the tensioner (1) comprises a dust cover (34) facing at least one radially inner portion (33) of the pulley (5) to prevent entry of external agents, and is radially centered with respect to the bearing (13).

Description

[0001] "TENSIONER FOR A BELT DRIVE"

[0002] Cross-Reference to Related Applications This Patent Application claims priority from Italian Patent Application No . 102024000029976 filed on December 24, 2024, the entire disclosure of which is incorporated herein by reference .

[0003] Technical Sector

[0004] The present invention relates to a tensioner for a belt drive . The present invention finds a preferred, although not exclusive, application in an accessory drive of an internal combustion engine of a motor vehicle, to which reference will be made below without losing generality.

[0005] PRIOR ART

[0006] As is known, the accessory drives of internal combustion engines of the motor vehicles comprise a first pulley adapted to be connected to a drive shaft, at least a second pulley connected to an accessory of the engine, for example an electric machine with the function of a current generator, and a belt cooperating with the pulleys to transmit torque from the first to the second pulley.

[0007] The drive may comprise further pulleys driven by the belt, for example for driving a compressor of an air conditioning system or a pump of the cooling liquid of the engine .In order to maintain a belt tension level higher than a predetermined minimum value and avoid consequent slippages, wear and unwanted noises, the accessory drives comprise at least one tensioner acting on the slack span of the belt which, in the simplest case where the electric machine is used only as a generator, is the span of the belt downstream of the first pulley (driving pulley) in the direction of rotation of the pulleys and the belt itself .

[0008] The tensioner, in its simplest form, comprises a base adapted to be fixed to a fixed support, for example the motor crankcase, an arm rotatable with respect to the base about a first axis, and a pulley carried by the arm and rotatable relative thereto about a second axis parallel to the axis of the arm. The pulley is adapted to cooperate with the belt by exerting a tensioning force under the thrust of a spring interposed between the base and the arm.

[0009] In the event that the electric machine is reversible, that is, it can be used both as a generator to charge the battery of the motor vehicle and as an electric motor to provide additional torque or start the heat engine, a dual arm tensioner acting on both spans of the belt is used, each of which can be tensioned or slack depending on the operating condition .

[0010] Various configurations are known for this purpose . In the so-called "V" tensioners, the arms are hinged ona common base, typically fixed to the crankcase of the IC engine within the path of the belt, and rotate about a common axis .

[0011] In the so-called "orbital" tensioners, the arms are mounted on an annular base, for example configured to be fixed to the electric machine, and are ring-shaped, so as to surround the pulley of the electric machine, and rotate between them and with respect to the base about a common axis (typically coincident with the axis of the electric machine) .

[0012] Intermediate solutions are also known wherein a first arm is annular and rotates about the axis of the electric machine, and the second arm is carried by the first arm and rotates with respect thereto about an eccentric axis with respect to the electric machine .

[0013] The configurations described above by way of example are not exhaustive, as other types of tensioners are known ( for example tensioners with linearly sliding arms or arms, hydraulic tensioners, etc . ) .

[0014] Whatever the solution adopted, the problem arises of mounting a pulley on a pivot fixed cantilevered on the (respective) arm, through one or two bearings, and of protecting the bearings from entry of external agents by means of a dust cover .

[0015] Exposure of the InventionAim of the present invention is the realization of a tensioner in which the dust cover can be mounted in a simple and economical way, and preferably in an automatic way, and in which the dust cover can be made economically, with not particularly tight dimensional tolerances, but can nevertheless effectively perform its function of protecting the bearing ( s ) .

[0016] The aforesaid aim is achieved by a tensioner according to claim 1 .

[0017] According to one embodiment of the invention, the dust cover comprises an inner edge disposed within an inner ring of the at least one bearing.

[0018] This facilitates the positioning of the dust cover during the mounting.

[0019] Preferably, the tensioner comprises two bearings axially adj acent to each other and interposed between the pivot and the pulley; a first bearing is centered on the arm and the dust cover is centered on the second bearing. In this way, the radial support of the pulley is improved, and the dust cover is indirectly centered on the arm.

[0020] Optionally, the bearings are mounted at least partially on a common bush radially interposed between the pivot and respective inner rings of the bearings themselves . In this way, the bearings can be pre-assembled on the bush and mounted on the arm as a pre-assembled unit .Preferably, the inner ring of the first bearing is mounted partially on the bushing and partially on a proj ection of the arm surrounding the pivot . The bushing is thus centered with respect to the arm.

[0021] Preferably, the inner ring of the second bearing is partially mounted on the bushing, and the inner edge of the dust cover is inserted into a portion of the inner ring of the second bearing extending beyond the bushing; the mounting of the dust cover on the second bearing is thereby facilitated .

[0022] Brief Description of the Drawings

[0023] For a better understanding of the invention, a preferred embodiment of the invention is described below with reference to the attached drawings, wherein:

[0024] Figure 1 is a perspective view of a tensioner of the drive of Figure 1 realized according to the invention;

[0025] Figure 2 is a plan view of the tensioner of Figure 1 ; Figure 3 is a section along line III-III of Figure 2 ; and

[0026] Figure 4 is an exploded and partial perspective view of the tensioner of Figure 1.

[0027] Description of an Example of Implementation of the Invention

[0028] With reference to the figures, 1 denotes as a whole a tensioner for an accessory drive of an internal combustionengine (not shown) .

[0029] The tensioner 1 comprises, in a known manner, a base 2 adapted to be fixed to a support structure 3, for example a motor crankcase, an arm 4 extending in a cantilevered manner from the base 2 and rotatable relative thereto about a first axis A, and a pulley 5 carried by the arm 4 at its own free end 6 and rotatable with respect to the arm 5 about a second axis B parallel to the axis A.

[0030] The arm 4 is provided with a hub 7 hinged to a pivot 8 of axis A fixed to the base 2 in a conventional manner and not described as not forming part of the invention.

[0031] The base 2 is substantially cup-shaped, and houses a spiral spring 9 having the respective ends constrained, in a known and not shown manner, to the base 2 and to the arm 4, so as to exert on the arm 4 a tensioning force adapted to push the pulley 5 against a belt of the accessory drive (not shown) .

[0032] With reference to Figures 2 and 3, the pulley 5 is hinged to the arm 4 by means of a pivot 10 of axis B fitted in a hole 11 obtained on the end 6 of the arm itself and a pair of ball bearings 12, 13 having respective inner rings 14, 15 and respective outer rings 16, 17 disposed axially in contact with each other .

[0033] The inner rings 14, 15 of the bearings 12, 13 are partially fitted on a bushing 18 in turn fitted on the pivot10. The bushing 18 is conveniently made of plastic material and has, in cross-section, a corrugated profile defined by a plurality of longitudinal ribs 19 alternated with grooves 20 (Figure 4 ) to favour a mounting by radial interference on the pivot 10 and inside the inner rings 14, 15 of the bearings 12, 13.

[0034] A portion of the inner ring 14 of the bearing 12 extending axially beyond the bushing 18 is fitted onto an axial cylindrical proj ection 24 of the arm 4 surrounding the hole 11.

[0035] The outer ring 16 of the bearing 12 is mounted inside the pulley 5, in axial contact with an inner shoulder 25 thereof .

[0036] The outer ring 17 of the bearing 13 is blocked against the outer ring 16 of the bearing 13 by an elastic ring 26.

[0037] The pulley 5, conveniently made of plastic material or aluminium alloy, integrally comprises an inner cylindrical hub 30, a cylindrical roller 31 externally coaxial to the hub 30, having an axial length greater than the hub 30, and a plurality of substantially radial ribs 32 integrally joining the hub 30 to the roller 31. Due to the greater axial extension of the roller 30 with respect to the hub 31, the ribs 32 have a substantially trapezoidal shape, with the oblique sides concave in such a way as to be connected with a head surface 33 of the hub 30 defining with it an innerportion of the substantially radial pulley 5.

[0038] Finally, the tensioner 1 comprises a dust cover 34 having a funnel shape and comprising an intermediate portion 35 of f rustoconical shape, from an end thereof with smaller diameter a flat annular flange 36 ending with cylindrical edge 37 extends radially inwards, and from an end thereof with larger diameter an outer collar 38 extends radially.

[0039] The edge 37 has an outer diameter smaller than or equal to the internal diameter of the inner ring 15 of the bearing 13 and is housed in the portion of the latter extending beyond the bushing 18.

[0040] The pivot 10 has a hexagonal end head 40 provided with a base flange 41, which is configured so as to clamp the annular flange 36 of the dust cover 37 against the inner ring 15 of the bearing 13 (Figure 3) .

[0041] The outer collar 38 of the dust cover 37 is disposed facing the radially inner portion of the pulley 5, at a reduced axial distance therefrom, so as to define with it a labyrinth seal that prevents, during use, entry of external agents towards the bearings 12, 13.

[0042] The operation of the tensioner 1 is known per se, and is not described in detail .

[0043] The use of a dust cover 34 centered on the bearing 13 allows the mounting to be carried out in a simple and easily automated manner .Since said cover is fixed, in use, and is centered with respect to the bearing 13, it can be made with a not particularly high precision by inj ection molding, if it is of plastic material, or by sheet metal molding.

[0044] The centering with respect to the inner ring 15 of the bearing 13 must not in fact be precise, it being sufficient that the clearance and tolerances are such as to ensure that there is no contact, in use, between the outer collar 38 of the cover and the pulley 5.

[0045] Finally, it is clear that modifications and variants can be made to the tensioner 1, which, however, do not fall outside the scope of protection defined by the claims .

[0046] For example, the type and configuration of the tensioner may be different; in particular, the tensioner may be a biarm tensioner, and the arms may be of any shape and configuration .

[0047] The spring may be of any type, for example helical, and may be replaced or supplemented by pushing means of another nature ( for example by a fluid under pressure) .

Claims

CLAIMS1 . A tensioner for a belt drive comprising a base ( 2 ) securable to a support structure ( 3 ) , at least one arm ( 4 ) constrained to the base and movable relative thereto , at least one pulley ( 5 ) carried by the arm ( 4 ) and rotatable relative thereto about its own axis (B ) , and thrust means ( 9 ) acting on the arm ( 4 ) to push the pulley ( 5 ) into contact with the belt , wherein the pulley ( 5 ) is mounted on the arm ( 4 ) by means of a pivot ( 10 ) coaxial to the pulley ( 5 ) and at least one bearing ( 12 , 13 ) , and a dust cover ( 34 ) facing at least a radially inner portion ( 33 ) of the pulley ( 5 ) and configured to prevent entry of external agents , wherein the dust cover ( 35 ) is radially centered with respect to said bearing ( 13 ) .2 . Tensioner as claimed in claim 1 , wherein the dust cover ( 34 ) includes an inner edge ( 37 ) disposed within an inner ring ( 15 ) of the bearing ( 13 ) .3 . Tensioner as claimed in claim 1 or 2 , comprising two bearings ( 12 , 13 ) axially adj acent to each other and interposed between the pivot ( 10 ) and the pulley ( 5 ) , a first bearing ( 12 ) of said bearings ( 12 , 13 ) being centered on the arm ( 4 ) , the dust cover ( 37 ) being centered on a second bearing ( 13 ) of said bearings ( 12 , 13 ) .4 . Tensioner as claimed in claim 3 , wherein said bearings ( 12 , 13 ) are at least partially mounted on a common bushing( 18 ) radially interposed between the pivot ( 10 ) and respective inner rings ( 14 , 15 ) of said bearings .5 . Tensioner as claimed in claim 4 , wherein the inner ring ( 14 ) of the first bearing ( 12 ) is mounted partially on the bushing ( 18 ) and partially on a proj ection ( 24 ) of the arm ( 4 ) surrounding the pivot ( 10 ) .6 . Tensioner as claimed in claim 4 or 5 , wherein the inner ring ( 15 ) of the second bearing ( 13 ) is partially mounted on the bushing ( 18 ) , and the inner edge ( 37 ) of the dust cover ( 34 ) is inserted into a portion of the inner ring ( 15 ) of the second bearing ( 13 ) extending beyond the bushing ( 18 ) .

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