Tensioner for an accessory drive of a motor vehicle and accessory drive including such a tensioner

Abstract

Tensioner for an accessory drive of a prime mover (2), the accessory drive (1) comprising at least a first pulley (11) connected to a drive shaft (12) of the prime mover (2), at least a second pulley (13) connected to an accessory (15) of the prime mover (2), and a belt (19) wound at least on the first pulley (11) and the second pulley (13), the tensioner (21) comprising: a base (22) configured to be fixed to a fixed support structure (23); at least a first arm (31) rotatable with respect to the base (22) about a first axis (A1); at least a first tensioning pulley (41) carried by the first arm (31) and rotatable with respect to the first arm (31) about a first pulley axis (PA1) parallel to the first axis (A1); elastic means (51) acting at least on the first arm (31) to push at least the first tensioning pulley (41) into contact with a respective span of the belt (19), wherein the base (22) comprises a base surface (71) configured to face towards said support structure (23) and at least one first appendage (81) extending from the base surface (71) and configured to abut against said fixed support structure (23), wherein the first appendage (81) has an extension in a direction parallel to the first axis (A1) dimensioned so as to define a predetermined distance (d) between a centre-line plane (P) of the first tensioning pulley (41) orthogonal to the first axis (A1) and said fixed support structure (23).

Description

[0001] "TENSIONER FOR AN ACCESSORY DRIVE OF A MOTOR VEHICLE AND ACCESSORY DRIVE INCLUDING SUCH A TENSIONER"

[0002] Cross-Reference to Related Applications This Patent Application claims priority from Italian Patent Application No . 102024000029955 filed on December 24, 2024, the entire disclosure of which is incorporated herein by reference .

[0003] Technical field

[0004] The present invention relates to a tensioner for an accessory drive of a motor vehicle and an accessory drive including such a tensioner .

[0005] Background art

[0006] As is known, an accessory drive for a prime mover, for example an internal combustion engine, comprises a first pulley connected to a drive shaft of the prime mover and a second pulley connected to a shaft of an accessory of the prime mover, for example a compressor of the air conditioning system. Optionally, the accessory drive comprises a third pulley connected to a shaft of an electrical machine and / or other pulleys for driving other accessories of the engine . The accessory drive further comprises a belt for the transmission of the motion between the aforementioned pulleys and a tensioner configured to ensure a correct minimum level of belt tension and prevent slippage between the belt and the pulleys .

[0007] The tensioner comprises a base configured to be fixed to a fixed support structure; at least a first arm rotatable with respect to the base about a first axis; at least a first tensioning pulley carried by the first arm and rotatable with respect to the first arm about a first pulley axisparallel to the first axis; and elastic means acting at least on the first arm to push at least the first tensioning pulley into contact with a respective span of the belt .

[0008] In conventional accessory drives, wherein the electrical machine is an alternator (electrical generator) driven by the engine, the tensioner acts on the slack span of the belt, i . e . the span located downstream of the engine and upstream of the alternator with reference to the direction of motion of the belt .

[0009] In motor vehicles, instead of the conventional alternator, a reversible electrical machine is increasingly being used which can operate, besides in the conventional generator mode, according to further modes, for example as a regenerative brake (so-called "recovery" condition) , or as supplementary motor acting in combination with the prime mover (so-called "boost" condition) .

[0010] The use of a reversible electrical machine means that the span of the belt which is tensioned in the operating conditions wherein the electrical machine is driven by the motor becomes the slack span when the driving torque is supplied by the electrical machine .

[0011] Therefore, various solutions have been developed which allow to ensure the correct tensioning of both spans of the belt .

[0012] For example, a solution consists in using a two-arm tensioner carrying respective tensioning pulleys . In particular, the tensioner further comprises a second arm rotatable about a second axis and a second tensioning pulley carried by the second arm and rotatable with respect to the second arm about a second pulley axis . The first arm and the second arm may be substantially rod-shaped or ring-shaped.Furthermore, the first axis and the second axis may be coincident with or distinct from each other .

[0013] The base comprises a substantially flat base wall configured to be fixed to the support structure and which is part of, or cooperates with, a casing configured to house the elastic means . For example, the base comprises such casing which is substantially cup-shaped and comprises the aforementioned base wall and a side wall extending from the base wall .

[0014] Conveniently, the first tensioning pulley (as well as the second tensioning pulley, if present) must be substantially aligned with the belt (i . e . the respective centre-line planes must be substantially coincident with each other) , as well as the pulleys of the accessory drive .

[0015] Typically, the distance between the support structure and the first tensioning pulley (as well as the second tensioning pulley, if present) is relatively small . However, if such distance is relatively large, the accessory drive becomes complicated since further components are needed which must be connected to the support structure and the tensioner to ensure that the first tensioning pulley (as well as the second tensioning pulley, if present) is substantially aligned with the belt . Furthermore, the mounting time and complexity increase, since these components must be positioned correctly and connected to the support structure and the tensioner .

[0016] A purpose of the present invention is to provide a tensioner for an accessory drive, which allows the above problems to be overcome .

[0017] Disclosure of the invention

[0018] The aforementioned purpose is achieved by a tensionerfor an accessory drive as claimed in claim 1.

[0019] The present invention further relates to an accessory drive as claimed in claim 15.

[0020] Brief description of the drawings

[0021] For a better understanding of the present invention, a preferred embodiment is described hereinafter, by way of non-limiting example and with reference to the accompanying drawings, wherein:

[0022] - Figure 1 is a schematic front view of an accessory drive with a tensioner according to a first embodiment of the present invention;

[0023] - Figure 2 is a schematic exploded perspective view of the tensioner of Figure 1 ;

[0024] - Figure 3 is a cross-sectional side view of a tensioner according to a second embodiment of the present invention; and

[0025] - Figure 4 is a perspective view of a component of the tensioner of Figure 3.

[0026] Detailed description of the invention With reference to Figure 1, there is indicated by 1 an accessory drive of a prime mover, for example an internal combustion engine 2 .

[0027] The accessory drive 1 comprises a first pulley 11 connected to a drive shaft 12 of the engine 2 and a second pulley 13 connected to a shaft 14 of an accessory 15 of the engine 2, for example a compressor of the air conditioning system. Optionally, the accessory drive 1 comprises a third pulley 16 connected to a shaft 17 of an electrical machine 18 and / or other pulleys for driving other accessories of the engine 2 .

[0028] The accessory drive 1 further comprises a belt 19 whichis wound on the pulleys 11, 13, 16 and thus has a first span 19a comprised between the first pulley 11 and the third pulley 16, a second span 19b comprised between the third pulley 16 and the second pulley 13, and a third span 19c comprised between the second pulley 13 and the first pulley 11 .

[0029] The accessory drive 1 further comprises a tensioner 21 comprising a base 22 configured to be fixed to a fixed support structure 23, at least a first arm 31 rotatable with respect to the base 22 about a first axis Al, at least a first tensioning pulley 41 carried by the first arm 31 and rotatable with respect to the first arm 31 about a first pulley axis PAI parallel to the first axis Al, and elastic means 51 acting at least on the first arm 31 to push at least the first tensioning pulley 41 into contact with a respective span of the belt 19.

[0030] In particular, the support structure 23 may be a bracket fixed to the engine 2 in an area inside or outside the belt 19, or a portion of the engine 2 itself in such an area, or a casing of the electrical machine 18. Therefore, the base 22 may be fixed internally or externally to the belt 19.

[0031] Conveniently, the elastic means 51 comprise a torsion spring 52 .

[0032] Preferably, the torsion spring 52 is a spiral spring extending substantially orthogonally to the first axis Al . In particular, the torsion spring 52 has an axis parallel to, and preferably coincident with, the first axis Al and the turns of the torsion spring 52 are intersected by a plane orthogonal to the first axis Al . Conveniently, the torsion spring 52 comprises a first end 61, which is an inner end (i . e . at a smaller distance from the axis of the torsionspring 52 ) , and a second end 62, which is an outer end (i . e . at a larger distance from the axis of the torsion spring 52 ) .

[0033] Preferably, the torsion spring 52 is shaped as a ribbon, i . e . it is made of a wire with a rectangular cross-section.

[0034] In a first embodiment (Figures 1 and 2 ) , the tensioner 21 further comprises a second arm 32 rotatable about a second axis A2 and a second tensioning pulley 42 carried by the second arm 32 and rotatable with respect to the second arm 32 about a second pulley axis PA2 .

[0035] In particular, the second pulley axis PA2 is parallel to the second axis A2 .

[0036] Conveniently, the second axis A2 is parallel to the first axis Al . Preferably, the first axis Al and the second axis A2 are coincident with each other and define a common axis A of rotation of the two arms 31, 32. Therefore, the first arm 31 and the second arm 32 are rotatable with respect to the base 22 about the common axis A. In particular, the first arm 31 and the second arm 32 are hinged to the base 22 about the common axis A.

[0037] In the first embodiment, the elastic means 51 are operatively interposed between the first arm 31 and the second arm 32 to push the first tensioning pulley 41 and the second tensioning pulley 42 into contact with respective spans 19a, 19b of the belt 19.

[0038] In particular, the first end 61 of the torsion spring 52 is coupled to the first arm 31 and the second end 62 of the torsion spring 52 is coupled to the second arm 32.

[0039] Conveniently, the tensioning pulleys 41, 42 are configured to cooperate respectively with the spans 19a, 19b of the belt 19 arranged respectively upstream and downstreamof the third pulley 16 according to the direction of advancement of the belt 19 itself (clockwise, with reference to Figure 1 ) .

[0040] In particular, the first arm 31 and the second arm 32 are biased towards each other by the torsion spring 52, and the tensioning pulleys 41, 42 are configured to cooperate with respective outer surfaces of the respective spans 19a, 19b of the belt 19.

[0041] In a second embodiment (Figures 3 and 4 ) , the first arm 31 is the only arm of the tensioner 21 and the first tensioning pulley 41 is the only tensioning pulley of the tensioner 21 .

[0042] In the second embodiment, the elastic means 51 are operatively interposed between the base 22 and the first arm 31 to push the first tensioning pulley 41 into contact with a respective span of the belt 19.

[0043] In particular, the first end 61 of the torsion spring 52 is coupled to the first arm 31 and the second end 62 of the torsion spring 52 is coupled to the base 22.

[0044] Conveniently, the first arm 31 is biased towards the belt 19 by the torsion spring 52 and the first tensioning pulley 41 is configured to cooperate respectively with an outer surface of the respective span of the belt 19.

[0045] The base 22 comprises a base surface 71 configured to face towards the support structure 23 and at least one first appendage 81 extending from the base surface 71 and configured to abut against the support structure 23. The first appendage 81 has an extension in a direction parallel to the first axis Al dimensioned so as to define a predetermined distance d between a centre-line plane P of the first tensioning pulley 41 orthogonal to the first axisAl and the support structure 23.

[0046] In particular, the base surface 71 is substantially orthogonal to the first axis Al and facing, in use, towards the support structure 23. The first appendage 81 extends from the base surface 71 and is shaped to be in contact, in use, with the support structure 23. Regardless of its specific shape, the extension of the first appendage 81 in a direction parallel to the first axis Al, i . e . the length of the first appendage 81 measured along the first axis Al, is such that the distance between the centre-line plane P (orthogonal to the first axis Al) of the first tensioning pulley 41 and the support structure 23 is equal to the aforementioned predetermined distance d.

[0047] Conveniently, the centre-line plane P of the first tensioning pulley 41 is the plane orthogonal to the first pulley axis PAI and which divides in half the first tensioning pulley 41 with reference to the extension of the first tensioning pulley 41 along the first pulley axis PAI .

[0048] Conveniently, the centre-line plane P of the first tensioning pulley 41 is the plane on which the resultant of the forces exchanged, in use, between the first tensioning pulley 41 and the belt 19 is located.

[0049] Conveniently, the aforementioned predetermined distance d is such that the centre-line plane P of the first tensioning pulley 41 coincides, in use, with the centre-line plane of the belt 19.

[0050] In particular, the extension of the first appendage 81 in the direction parallel to the first axis Al depends on the position (in particular the distance along the first axis Al ) of the first tensioning pulley 41 with respect to the base surface 71, and is chosen so that the centre-lineplane P of the first tensioning pulley 41 coincides, in use, with the centre-line plane of the belt 19. In other words, the extension of the first appendage 81 in the direction parallel to the first axis Al is chosen in such a way as to distance the first tensioning pulley 41 from the support surface 23 so as to make the centre-line plane P of the first tensioning pulley 41 coincide, in use, with the centre-line plane of the belt 19. Conveniently, the centre-line plane P of the first tensioning pulley 41 also coincides, in use, with the respective centre-line planes of the pulleys 11, 13, 16.

[0051] Preferably, the first appendage 81 is monolithic with the base surface 71.

[0052] In particular, the base surface 71 and the first appendage 81 are made in one piece, i . e . they belong to a single piece of the base 22. In other words, the base 22 comprises an end portion defined by the first appendage 81.

[0053] For example, the base 22 (comprising the base surface 71 and the first appendage 81 ) is made by moulding.

[0054] Preferably, the first appendage 81 extends parallel to the first axis Al .

[0055] For example, the first appendage 81 is shaped as a cylinder of axis Al, optionally hollow (i . e . defining an inner cavity) , or as a prism of axis Al, optionally hollow (i . e . defining an inner cavity) .

[0056] In an embodiment (not illustrated) , the at least one first appendage 81 comprises a plurality of proj ections, for example three proj ections, extending from the base surface 71 parallel to the first axis Al . Conveniently, such proj ections have substantially the same shape . For example, each proj ection is shaped as a prism whose axis is parallelto the first axis Al or as a cylinder whose axis is parallel to the first axis Al .

[0057] Preferably, the first appendage 81 is substantially tubular .

[0058] In particular, the first appendage 81 is shaped as a sleeve, i . e . it defines a substantially cylindrical inner cavity. Preferably, the first appendage 81 is shaped as a hollow cylinder of axis Al .

[0059] Preferably (Figures 3 and 4 ) , the base 22 comprises a second appendage 82 extending from the base surface 71 and configured to abut against the support structure 23.

[0060] In particular, the second appendage 82 extends from the base surface 71 and is shaped so as to be in contact, in use, with the support structure 23.

[0061] Preferably, the second appendage 82 is monolithic with the base surface 71.

[0062] In particular, the base surface 71 and the second appendage 82 are made in one piece, i . e . they belong to a single piece of the base 22. In other words, the base 22 comprises an end portion defined by the second appendage 82.

[0063] For example, the base 22 (which comprises the base surface 71, the first appendage 81 and the second appendage 82 ) is made by moulding.

[0064] Preferably, the second appendage 82 extends parallel to the first axis Al .

[0065] For example, the second appendage 82 is shaped as a prism of axis Al, optionally hollow (i . e . defining an inner cavity) , or as a cylinder of axis Al, optionally hollow (i . e . defining an inner cavity) .

[0066] Preferably, the second appendage 82 is substantially tubular .In particular, the second appendage 82 is shaped as a sleeve, i . e . it defines a substantially cylindrical inner cavity. Preferably, the second appendage 82 is shaped as a hollow cylinder of axis Al .

[0067] Preferably, the first appendage 81 and the second appendage 82 jointly define an annular chamber 83 interposed between the first appendage 81 and the second appendage 82.

[0068] In particular, the first appendage 81 is tubular and the second appendage 82 is tubular . Preferably, the first appendage 81 and the second appendage 82 are coaxial, i . e . they define two hollow cylinders of axis Al, one relatively external (i . e . the hollow cylinder having a larger outer diameter) and one relatively inner (i . e . the hollow cylinder having a smaller outer diameter) . The annular chamber 83 is the cavity, substantially shaped as a hollow cylinder of axis Al, interposed between the first appendage 81 and the second appendage 82.

[0069] Preferably, the base 22 comprises at least one connecting portion 91 configured to connect the first appendage 81 and the second appendage 82.

[0070] In particular, the at least one connecting portion 91 extends from the base surface 71 or is spaced apart from the base surface 71. For example, the at least one connecting portion 91 is shaped as a rod or shaped as a plate, e . g. an annular plate .

[0071] For example, the at least one connecting portion 91 comprises a single (substantially annular) plate extending substantially orthogonally to the first axis Al and configured to connect the first appendage 81 and the second appendage 82, or a plurality of ( substantially annular) plates extending substantially orthogonally to the firstaxis Al and each configured to connect the first appendage 81 and the second appendage 82. For example, such plates are equidistant from each other along the first axis Al .

[0072] Preferably, each connecting portion 91 extends substantially along a plane containing the first axis Al .

[0073] In particular, the at least one connecting portion 91 comprises at least one plate 92 extending substantially along a plane containing the first axis Al . Conveniently, the at least one connecting portion 91 comprises a plurality of plates 92 and each plate 92 extends substantially along a plane containing the first axis Al . Preferably, such plates 92 extend from the base surface 71. Conveniently, such plates 92 are angularly equispaced from each other .

[0074] In the first embodiment (Figures 1 and 2 ) , the base 22 comprises a base plate 101 and a tubular axial pivot 102 of axis Al fixed to the plate 101.

[0075] Conveniently, the plate 101 comprises the aforementioned base surface 71, from which the at least one first appendage 81 extends, and an axially opposite surface 103 from which the pivot 102 extends .

[0076] In particular, the first appendage 81 is monolithic with the plate 101 .

[0077] Conveniently, the first appendage 81 extends parallel to the first axis Al and is substantially tubular . Preferably, the plate 101 is substantially circular, in particular it is shaped as a disc of axis Al, and the first appendage 81 is shaped as a hollow cylinder of axis Al having an outer diameter equal to the diameter of the plate 101.

[0078] The first arm 31 and the second arm 32 are hinged on the pivot 102 with interposition of a radial anti-friction bushing 111.The first arm 31 is provided with a hub 121 having a substantially circular end, which has on a face thereof a proj ecting circumferential edge 122 configured to surround, in use, the plate 101 of the base 22. From the hub 121, in particular from an axially opposite side with respect to the edge 122, there extends an axial tubular sleeve 123 rotatable on the bushing 111 and having the dual purpose of resisting tilting moments and of providing an anchor for the first end 61 of the torsion spring 52.

[0079] The second arm 32 is provided with a substantially cupshaped hub 131, which is hinged on the bushing 111 and forms with the hub 121 of the first arm 31 an annular cavity housing the torsion spring 52 and radially delimited by a cylindrical wall 132 extending axially cantilevered from the second arm 32 to the first arm 31. The wall 132 defines an anchor for the second end 62 of the torsion spring 52.

[0080] Optionally, the tensioner 21 further comprises stop means 141 configured to limit an angular distance between the first arm 31 and the second arm 32.

[0081] For example, the stop means 141 comprise a first radial proj ection 151 extending from the first arm 31 and a second radial proj ection 152 extending from the second arm 32. In particular, the first proj ection 151 extends radially from the hub 121 and the second projection 152 extends radially from the wall 132. Preferably, the stop means 141 further comprise at least one removable stop element 161 so as to define a first maximum angular distance between the two arms 31, 32 in an installation configuration of the belt 19 wherein the removable stop element 161 is absent, and a second maximum angular distance, smaller than the first maximum angular distance, in an operating configuration ofthe accessory drive 1 wherein the removable stop element 161 is present .

[0082] For example, the removable stop element 161 comprises a pin 162 fixable to the support structure 23. In particular, the pin 162 comprises a hollow cylindrical element 163 of axis B, parallel to axis A, fixable to the support structure 23 via removable connection means, for example a screw 164 of axis B passing through the cylindrical element 163 and engaging a respective threaded hole of the support structure 23. Preferably, the pin 162 comprises an elastic coating 165, for example shaped as a hollow cylinder of axis B .

[0083] In the first embodiment (Figure 2 ) , the tensioner 21 further comprises an anti-friction ring 171 axially interposed between the first arm 31 on one side and, on the other side, the second arm 32 and the torsion spring 52, so as to reduce as much as possible the relative friction between the first arm 31 and the second arm 32 ; an axial blocking ring 172 fixed on a free end of the pivot 102 via plastic deformation thereof ; a pair of annular elements 173, 174 in plastic material axially interposed one between the plate 101 of the base 22 and the first arm 31 and the other one between the second arm 32 and the blocking ring 172 to define the damping characteristic of the oscillations of the arms 31, 32 ; a cup spring 175 arranged between the second arm 32 and the annular element 174 and configured to keep the group in axial tension recovering the clearances .

[0084] The tensioning pulleys 41, 42 are mounted idle, via respective bearings (not illustrated) , on respective free ends 181, 182 of the arms 31, 32.

[0085] Conveniently, a centre-line plane of the second tensioning pulley 42 orthogonal to the second axis A2 (andthus orthogonal to the first axis Al ) is substantially coincident with the centre-line plane P of the first tensioning pulley 41 orthogonal to the first axis Al and thus, in use, with the centre-line plane of the belt 19.

[0086] The tensioner 21 is mountable on the support structure 23 via a screw 191 passing through the pivot 102. Preferably, the base 22 has a tooth (not illustrated) configured to engage a respective seat of the support structure 23 to prevent rotation of the base 22 about the axis A.

[0087] In the second embodiment (Figures 3 and 4 ) , the base 22 comprises a casing 93 extending along the first axis Al from opposite side to the first appendage 81 with respect to the base surface 71 and configured to at least partially house the elastic means 51.

[0088] In particular, the casing 93 is substantially cup-shaped and comprises a base plate 201, extending substantially orthogonally to the first axis Al, and a side wall 202 extending axially from the plate 201. Preferably, the plate 201 is substantially circular and the side wall 202 is substantially cylindrical of axis Al . Conveniently, the side wall 202 defines an anchor for the second end 62 of the torsion spring 52.

[0089] Conveniently, the base 22 comprises a tubular axial pivot 203 of axis Al fixed to the plate 201 and extending from opposite side to the first appendage 81.

[0090] Conveniently, the plate 201 comprises the aforementioned base surface 71, from which the at least one first appendage 81 extends, and an axially opposite surface 204 which faces the elastic means 51, in particular the torsion spring 52.

[0091] In particular, the first appendage 81 is monolithic with the plate 201 .Conveniently, the first appendage 81 extends parallel to the first axis Al and is substantially tubular . Preferably, the first appendage 81 is shaped as a hollow cylinder of axis Al having an outer diameter equal to the diameter of the plate 201 .

[0092] Conveniently, the second appendage 82 also extends from the plate 201 .

[0093] In particular, the second appendage 82 is monolithic with the plate 201.

[0094] Conveniently, the second appendage 82 extends parallel to the first axis Al and is substantially tubular . Preferably, the second appendage 82 is shaped as a hollow cylinder of axis Al and has a thickness (i . e . an extension in a direction orthogonal to the first axis Al ) substantially equal to the thickness of the first appendage 81.

[0095] Conveniently, the first appendage 81 is relatively external (i . e . at a greater distance from the first axis Al ) and the second appendage 82 is relatively internal (i . e . at a smaller distance from the first axis Al ) .

[0096] Preferably, the second appendage 82 is, at least partially, axially (i . e . in the direction of the first axis Al ) overlapping the pivot 203, so as to define an axial extension of the pivot 203.

[0097] Conveniently, the base 22 also comprises the at least one connecting portion 91, in particular six plates 92 such that each plate extends substantially along a plane containing the first axis Al . The six plates 92 extend from the base surface 71 and are angularly equispaced from each other so as to divide the annular chamber 83 into six parts substantially equal to each other .

[0098] The first arm 31 is hinged on the pivot 203 withinterposition of a radial anti-friction bushing 211.

[0099] The first arm is provided with a hub 221 substantially cup-shaped and comprising a plate 222, extending substantially orthogonally to the first axis Al, and a side wall 223 extending axially from the plate 222 and facing the side wall 202 of the base 22. Preferably, the plate 222 is substantially annular and the side wall 223 of the hub 221 is substantially cylindrical of axis Al and has an outer diameter equal to the outer diameter of the side wall 202 of the base 22. From the hub 221, in particular from the inner circumferential edge of the plate 222, there extends an axial tubular sleeve 224 rotatable on the bushing 211 and having the twofold purpose of resisting tilting moments and of providing an anchor for the first end 61 of the torsion spring 52. In particular, the sleeve 224 has a free end 225 arranged in an annular groove 226 present on the surface 204 of the plate 201.

[0100] In the second embodiment (Figure 3) , the tensioner 21 further comprises an anti-friction ring 231 interposed axially between the first arm 31 on and one side, on the other side, the base 22 and the torsion spring 52, so as to reduce as much as possible the relative friction between the first arm 31 and the base 22 ; a blocking ring 232 arranged at a free end of the pivot 203; a pair of annular elements 233, 234 in plastic material interposed radially between the base 22 and the first arm 31, in particular one between the plate 201 of the base 22 and the free end 225 of the sleeve 224 of the first arm 31, and the other one between the free end of the pivot 203 of the base 22 and the plate 222 of the first arm 31 ; a cup spring 235 arranged between the first arm 31 and the blocking ring 232 and configured to keep thegroup in axial tension recovering the clearances .

[0101] The first tensioning pulley 41 is mounted idle, via one or more bearings 241 ( for example, one or more single-row ball bearings or double-row ball bearings) , on a free end 242 of the first arm 31. In particular, the bearings 241 comprise two ball bearings (each being a single-row ball bearing) overlapping along the first pulley axis PAI . Conveniently, the centre-line plane P of the first tensioning pulley 41 is orthogonal to the first pulley axis PAI and interposed between the two bearings 241.

[0102] The tensioner 21 is mountable on the support structure 23 via a screw 251 passing through the pivot 203. Preferably, the base 22 has a tooth 261 configured to engage a respective seat of the support structure 23 to prevent rotation of the base 22 about the first axis Al . Conveniently, the tooth extends along an axis parallel to, and distinct from, the first axis Al . In particular, the tooth 261 is arranged substantially at the intersection between the first appendage 81 and one of the six plates 92.

[0103] The operation of the tensioner 21 is the following.

[0104] In the first embodiment, the tensioner 21 is mounted on the support structure 23 by fixing the base 22 to the support structure 23, in particular via the screw 191, so that the base surface 71 faces towards the support structure 23 and the at least one first appendage 81 abuts against the support structure 23. Preferably, the tooth (not illustrated) of the base 22 engages the respective seat of the support structure 23 to prevent rotation of the base 22 about the axis A. The current configuration is the installation configuration of the belt 19, wherein the removable stop element 161 is absent . Therefore, the two arms 31, 32 can be angularlyspaced from each other to easily install the belt 19, so that the tensioning pulleys 41, 42 are outside the respective spans 19a, 19b . After installing the belt 19, the tensioner 21 moves, under the action of the torsion spring 52 , into a nominal position, defined by the balance between the pull of the belt 19 and the restoring force of the torsion spring 52. Conveniently, the centre-line plane P of the first tensioning pulley 41, as well as the centre-line plane of the second tensioning pulley 42, coincides with the centreline plane of the belt 19. Preferably, the removable stop element 161 is subsequently inserted to limit an angular distance between the first arm 31 and the second arm 32. For example, the pin 162 is fixed to the support structure 23 via the screw 164. The current configuration is the operating configuration of the accessory drive 1, wherein the removable stop element 161 is present . Under normal operating conditions, the engine 2 supplies driving torque and the electrical machine 18 is driven and operates as an alternator . In this condition, the span 19a of the belt 19 is the slack span and the span 19b of the belt is the tensioned span. Under the thrust of the torsion spring 52, tending to bring the tensioning pulleys 41 and 42 closer together, the tensioning pulley 41 acts on the slack span 19a maintaining therein a predetermined minimum tension value when the torque varies . In boost mode, the electrical machine 18 supplies driving power (positive torque) which adds to that of the engine 2. This tends to reduce tension in the span 19b and increase tension in the span 19a of the belt 19. Conversely, in recovery mode the electrical machine 18 absorbs mechanical power (negative torque) , and thus the tension in the span 19a of the belt 19 tends to decrease .In the second embodiment, the tensioner 21 is mounted on the support structure 23 by fixing the base 22 to the support structure 23, in particular via the screw 251, so that the base surface 71 faces towards the support structure 23 and the at least one first appendage 81 abuts against the support structure 23. Conveniently, also the second appendage 82 abuts against the support structure 23. Preferably, the tooth 261 of the base 22 engages the respective seat of the support structure 23 to prevent rotation of the base 22 about the first axis Al . The current configuration is the installation configuration of the belt 19, i . e . the tensioner 21 is kept (e . g. by removable blocking means) in an installation position where the offset of the arm 31 with respect to the belt 19 is maximum, which can then be easily installed. After installing the belt 19, the tensioner 21 moves, under the action of the torsion spring 52, into a nominal position, defined by the balance between the pull of the belt 19 and the restoring force of the torsion spring 52. Conveniently, the centre-line plane P of the first tensioning pulley 41 coincides with the centre-line plane of the belt 19. Subsequently, under the thrust of the torsion spring 52, the tensioning pulley 41 acts on the belt 19 to maintain a predetermined minimum tension value .

[0105] Upon examination of the characteristics of the tensioner 21, the advantages of the present invention are evident .

[0106] In particular, the at least one appendage 81 of the base 22 of the tensioner 21 allows to have the first tensioning pulley 41 (as well as the second tensioning pulley 42, if present) substantially aligned with the belt 19 (i . e . the centre-line plane P of the first tensioning pulley 41 substantially coincident with the centre-line plane of thebelt 19) without using further components, thus simplifying the accessory drive 1 and reducing mounting time and complexity .

[0107] If present, the spiral torsion spring 52 extending substantially orthogonally to the first axis Al allows to reduce the footprint along the first axis Al .

[0108] If present, the annular chamber 83 interposed between the first appendage 81 and the second appendage 82 allows to reduce the material used for the base 22, and thus the weight of the tensioner 21.

[0109] If present, the at least one connecting portion 91 allows to increase the structural strength of the base 22.

[0110] Finally, it is clear that modifications may be made to the tensioner 21 without departing from the scope of protection defined by the claims .

[0111] For example, the internal combustion engine may be replaced by a prime mover of different nature, for example an electrical motor .

[0112] The base 22 may have any shape, for example it may be polygonal instead of circular in shape .

[0113] The at least one first appendage 81 may comprise a plurality of proj ections, for example three proj ections, extending from the base surface 71 obliquely with respect to the first axis Al .

[0114] If present, the spiral torsion spring 52 extending substantially orthogonally to the first axis Al may be made with a circular or square cross-section wire .

[0115] If the second arm 32 is present, the first axis Al and the second axis A2 may be distinct from each other . For example, the first axis Al may be stationary with respect to the base 22 and the second axis A2 may be stationary withrespect to the first arm 31. In such a case, the second arm 32, which is rotatable about the second axis A2, is rotatable with respect to, and preferably carried by, the first arm 31 .

[0116] The first arm 31 and the second arm 32 may be substantially ring-shaped instead of rod-shaped.

Claims

CLAIMS1 . Tensioner for an accessory drive of a prime mover ( 2 ) , the accessory drive ( 1 ) comprising at least a first pulley ( 11 ) connected to a drive shaft ( 12 ) of the prime mover ( 2 ) , at least a second pulley ( 13 ) connected to an accessory ( 15 ) of the prime mover ( 2 ) , and a belt ( 19 ) wound at least on the first pulley ( 11 ) and the second pulley ( 13 ) , the tensioner ( 21 ) comprising :- a base ( 22 ) configured to be fixed to a fixed support structure ( 23 ) ;- at least a first arm ( 31 ) rotatable with respect to the base ( 22 ) about a first axis (Al ) ;- at least a first tensioning pulley ( 41 ) carried by the first arm ( 31 ) and rotatable with respect to the first arm ( 31 ) about a first pulley axis ( PAI ) parallel to the first axis (Al ) ;- elastic means ( 51 ) acting at least on the first arm ( 31 ) to push at least the first tensioning pulley ( 41 ) into contact with a respective span of the belt ( 19 ) , wherein the base ( 22 ) comprises a base surface ( 71 ) configured to face towards said fixed support structure ( 23 ) and at least one first appendage ( 81 ) extending from the base surface ( 71 ) and configured to abut against said fixed support structure ( 23 ) , wherein the first appendage ( 81 ) has an extension in a direction parallel to the first axis (Al ) dimensioned so as to define a predetermined distance ( d) between a centre-line plane ( P ) of the first tensioning pulley ( 41 ) orthogonal to the first axis (Al ) and said fixed support structure ( 23 ) .2 . Tensioner as claimed in claim 1 , wherein the firstappendage ( 81 ) is monolithic with the base surface ( 71 ) . 3 . Tensioner as claimed in claim 1 or 2 , wherein the first appendage ( 81 ) extends parallel to the first axis (Al ) .4 . Tensioner as claimed in claim 3 , wherein the first appendage ( 81 ) is substantially tubular .5 . Tensioner as claimed in any of the preceding claims , wherein the base ( 22 ) comprises a second appendage ( 82 ) extending from the base surface ( 71 ) and configured to abut against said fixed support structure ( 23 ) .6 . Tensioner as claimed in claim 5 , wherein the second appendage ( 82 ) is monolithic with the base surface ( 71 ) .7 . Tensioner as claimed in claim 5 or 6 , wherein the second appendage ( 82 ) extends parallel to the first axis (Al ) .8 . Tensioner as claimed in claim 7 , wherein the second appendage ( 82 ) is substantially tubular .9 . Tensioner as claimed in claim 8 when dependent on claim 4 , wherein the first appendage ( 81 ) and the second appendage ( 82 ) j ointly define an annular chamber ( 83 ) interposed between the first appendage ( 81 ) and the second appendage ( 82 ) .10 . Tensioner as claimed in any of claims 5 to 9 , wherein the base ( 22 ) comprises at least one connecting portion ( 91 ) conf igured to connect the first appendage ( 81 ) and the second appendage ( 82 ) .11 . Tensioner as claimed in claim 10 , wherein each connecting portion ( 91 ) extends substantially along a plane containing the first axis (Al ) .12 . Tensioner as claimed in any of the preceding claims , comprising :- a second arm ( 32 ) rotatable about a second axis (A2 ) ;- a second tensioning pulley ( 42 ) carried by the second arm ( 32 ) and rotatable with respect to the second arm ( 32 ) about a second pulley axis ( PA2 ) ,wherein the elastic means ( 51 ) are operatively interposed between the first arm ( 31 ) and the second arm ( 32 ) to push the first tensioning pulley ( 41 ) and the second tensioning pulley ( 42 ) into contact with respective spans ( 19a, 19b ) of the belt ( 19 ) .13 . Tensioner as claimed in any of the preceding claims , wherein the elastic means ( 51 ) comprise a spiral torsion spring ( 52 ) extending substantially orthogonally to the first axis (Al ) .14 . Tensioner as claimed in any of the preceding claims , wherein the base ( 22 ) comprises a casing ( 93 ) extending along the first axis (Al ) from opposite side to the first appendage ( 81 ) with respect to the base surface ( 71 ) and configured to at least partially house the elastic means ( 51 ) .15 . Accessory drive for a prime mover, comprising at least a first pulley ( 11 ) connected to a drive shaft ( 12 ) of the prime mover ( 2 ) , at least a second pulley ( 13 ) connected to an accessory ( 15 ) of the prime mover ( 2 ) , a belt ( 19 ) wound at least on the first pulley ( 11 ) and the second pulley ( 13 ) , and a tensioner ( 21 ) as claimed in any of the preceding claims .

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