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

Abstract

Tensioner for an accessory drive of an internal combustion engine (2), the accessory drive (1) comprising at least a first pulley (3) connected to a drive shaft (4) of the engine (2), at least a second pulley (5) connected to an electrical machine (7), and a belt (8) wound at least on the first pulley (3) and the second pulley (5), the tensioner (11) comprising: a base (12) configured to be fixed to one of the engine (2) and a casing (13) of the electrical machine (7); a first arm (21) rotatable with respect to the base (12) about a first axis (A1); a second arm (22) rotatable with respect to the base (12) about a second axis (A2); a first tensioning pulley (31) carried by the first arm (21) and rotatable with respect to it about its own axis (PA1); a second tensioning pulley (32) carried by the second arm (22) and rotatable with respect to it about its own axis ( PA2); and elastic means (71) acting on the first arm (21) and on the second arm (22) to push the first tensioning pulley (31) and the second tensioning pulley (32) into contact with respective spans (8a, 8b) of the belt (8), the elastic means (71) comprising a traction spring (72) comprising a main body (73) extending along a spring axis (SA), a first end (81) operatively interposed between the main body (73) and the first arm (21), a second end (82) operatively interposed between the main body (73) and the second arm (22), wherein the main body (73), the first end (81) and the second end (82) are distinct elements.

Description

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

[0002] Cross-Reference to Related Applications

[0003] This Patent Appl ication claims priority from Italian Patent Application No . 102022000026268 filed on December 21 , 2022 , the entire disclosure of which is incorporated herein by reference .

[0004] Technical field

[0005] The present invention relates to a tensioner for an accessory drive o f a motor vehicle and to an accessory drive including such a tensioner .

[0006] Background art

[0007] As is known, an accessory drive of an internal combustion engine comprises a first pulley connected to a drive shaft of the engine , a second pulley connected to a shaft of an electrical machine , and may comprise one or more pulleys for driving other accessories , for example the compressor of the conditioning system . The accessory drive further comprises a belt for transmitting motion between the aforementioned pulleys and a tensioner configured to ensure a correct minimum tension level of the belt and preventing slippage between the belt and the pulleys .

[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 positioned downstream of the engine and upstream of the alternator with reference to the motion direction 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 regenerative brake ( the so-called "recovery" condition ) , or as supplementary motor acting in combination with the internal combustion engine ( the so-called "boost" condition) .

[0010] The use of a reversible electrical machine entails that the span of the belt which i s taut in the operating conditions wherein the electrical machine is driven by the engine becomes the slack span when the drive 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 .

[0013] In particular, according to a known solution, the tensioner comprises a base configured to be fixed to one of the engine and a casing of the electrical machine ; a first arm rotatable with respect to the base about a first axis ; a second arm rotatable with respect to the base about a second axis ; a first tensioning pulley carried by the first arm and rotatable with respect to it about its own axis ; a second tensioning pulley carried by the second arm and rotatable with respect to it about its own axis ; elastic means acting on the first arm and on the second arm for pushing the first tensioning pulley and the second tensioning pulley into contact with respective spans of the belt .

[0014] 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 one another .

[0015] The elastic means may comprise a traction spring . In such a case , the spring has respective hook-shaped ends hooked to the first arm and to the second arm, respectively . In order to allow installation o f the belt , the first arm and the second arm have to be suf f iciently angularly spaced apart from one another , subj ecting the ends of the traction spring to high strains . Such ends are subj ect to high stresses also in use . Clearly, a deterioration or even a breakage of the ends of the spring compromises the operation of the tensioner and thus of the accessory drive .

[0016] A purpose of the present invention is to manufacture 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 tensioner for an accessory drive as claimed in claim 1 .

[0019] The present invention further relates to an accessory drive as claimed in claim 16 .

[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 top schematic view of an engine provided with an accessory drive with a tensioner according to the present invention;

[0023] - Figure 2 is a front schematic view of the accessory drive of Figure 1 ;

[0024] - Figure 3 is a front view of the tensioner of Figure 1 ; - Figure 4 is an exploded perspective view of the tensioner of Figure 1 ;

[0025] - Figure 5 is a section view of a spring of the tensioner of Figure 1 ; and

[0026] - Figure 6 is an exploded view of the spring of Figure 5 .

[0027] Detailed description of the invention

[0028] With reference to Figures 1 and 2 , there is indicated by 1 an accessory drive of an internal combustion engine 2 .

[0029] The accessory drive 1 comprises a first pulley 3 connected to a drive shaft 4 of the engine 2 , of axis EA, a second pulley 5 connected to a shaft 6 of an electrical machine 7 , of axis MA, and a belt 8 which connects the first pulley 3 and the second pulley 5 to one another . The accessory drive may comprise other pulleys (not illustrated) for driving other accessories of the engine 2 , such as for example a compressor of the conditioning system .

[0030] The accessory drive 1 further comprises a tensioner 11 mounted on the electrical machine 7 and comprising a base 12 configured to be fixed to a casing 13 of the electrical machine 7 , a first arm 21 rotatable with respect to the base 12 about a first axis Al , a second arm 22 rotatable with respect to the base 12 about a second axis A2 , a first tensioning pulley 31 carried by the first arm 21 and rotatable with respect to it about its own axis PAI , and a second tensioning pulley 32 carried by the second arm and rotatable with respect to it about its own axis PA2 .

[0031] In the illustrated embodiment ( Figure 3 ) , the first arm 21 comprises a first ring 41 , rotatable with respect to the base 12 about the axis Al , and the second arm 22 comprises a second ring 42 , rotatable with respect to the base 12 about the axis A2 .

[0032] In particular ( Figure 4 ) , the base 12 integrally comprises a flat flange 51 configured to be fixed to the casing 13 of the electrical machine 7 and an annular collar 52 , of axis Al coincident in use with the axis MA, axially extending cantilevered from the flange 51 .

[0033] The first ring 41 is rotatably supported on the base 12 about the collar 52 via a first bushing 53 having a flat annular portion 54 axially interposed between the first ring 41 and the flange 51 and a cylindrical portion 55 , of axis Al , radially interposed between the first ring 41 and the collar 52 .

[0034] The second ring 42 is rotatably supported on the base 12 about the first ring 41 via a second bushing 56 .

[0035] The base 12 and the rings 41 , 42 have an inner diameter greater than the diameter of the second pulley 5 so as to allow to mount the tensioner 11 on the electrical machine 7 in the presence of the second pulley 5 .

[0036] The first ring 41 comprises an outer radial appendage 61 rotatably supporting the first pulley 31 of the tensioner 11 , of axis PAI , via a pivot 62 and a bearing 63 . The second ring 42 comprises an axial tubular appendage 64 , extending cantilevered from the opposite side of the flange 51 of the base 12 , on which the second pulley 32 of the tensioner 11 , of axis PA2 , is rotatably mounted via a pivot 65 and a bearing 66 .

[0037] The first pulley 31 and the second pulley 32 are configured to cooperate with respective spans 8a, 8b of the belt 8 arranged, respectively, downstream and upstream of the second pulley 5 according to the advancement direction of the belt 8 ( clockwise , with reference to Figure 2 ) . In the illustrated embodiment , the second ring 42 rotates with respect to the first ring 41 about the axis A2 which is parallel to the axis Al and distinct therefrom . The axis A2 is arranged inside the first ring 41 and orbits about the axis Al as the first ring 41 rotates .

[0038] The tensioner 1 further comprises elastic means 71 acting on the first arm 21 and on the second arm 22 for pushing the first pulley 31 and the second pulley 32 into contact with the respective spans 8a, 8b of the belt 8 .

[0039] The elastic means 71 comprise a traction spring 72 ( Figures 5 and 6 ) comprising a main body 73 extending along a spring axis SA, a first end 81 operatively interposed between the main body 73 and the first arm 21 , and a second end 82 operatively interposed between the main body 73 and the second arm 22 .

[0040] The main body 73 , the first end 81 and the second end 82 are distinct elements . In other words , the first end 81 and the second end 82 are distinct from one another and from the main body 73 , instead of being made in one single piece , i . e . monolithically, with it .

[0041] The purpose of the spring 72 is to generate an elastic force tending to keep the pulleys 31 , 32 in contact with the belt 8 and thus to keep, in use , a predetermined tension level in the belt 8 .

[0042] The spring 72 is arranged tangentially with respect to the first ring 41 and to the second ring 42 , and the spring axis SA is substantially orthogonal to the first axis Al and to the second axis A2 .

[0043] Conveniently, the main body 73 of the spring 72 is a helical spring made from a wire having a constant diameter .

[0044] The main body 73 comprises a first terminal portion 91 configured to cooperate with the first end 81 , a second terminal portion 92 configured to cooperate with the second end 82 , and a central portion 93 interposed between the first terminal portion 91 and the second terminal portion 92 .

[0045] In particular, the central portion 93 is a cylindrical helix, i . e . it extends along a cylinder whose axis is the spring axis SA.

[0046] The first terminal portion 91 is tapered and the second terminal portion 92 is tapered . In particular, the dimension transversal to the spring axis SA of the first terminal portion 91 and of the second terminal portion 92 progressively reduces as it moves away from the central portion 93 . Preferably, the first terminal portion 91 and the second terminal portion 92 extend along respective cones , in particular right circular cones , having bases coincident with the respective bases of the aforementioned cylinder .

[0047] The first end 81 of the spring 72 comprises a first coupling element 101 configured to hook to the first arm 21 , in particular to the first ring 41 , and the second end 82 of the spring 72 comprises a second coupling element 102 configured to hook to the second arm 22 , in particular to the second ring 42 .

[0048] Conveniently, the first arm 21 and the second arm 22 comprise respective pins 111 , 112 , and the first coupling element 101 and the second coupling element 102 comprise respective external portions 101a, 102a, arranged externally to the main body 73 , hook-shaped and configured to hook to the respective pins 111 , 112 .

[0049] In particular, the first arm 21 and the second arm 22 comprise respective external radial appendages 121 , 122 from which the respective pins 111 , 112 axially extend . Conveniently, the angular distance along the first ring 41 between the axis PAI and the pin 111 of the first arm 21 is substantially equal to the angular distance along the second ring 42 between the axis PA2 and the pin 112 of the second arm 22 .

[0050] The first coupling element 101 and the second coupling element 102 comprise respective internal portions 101b, 102b, arranged internally to the main body 73 and configured to positively couple to the respective terminal portions 91 , 92 , and respective intermediate portions 101c, 102c interposed between the respective external portions 101a, 102a and the respective internal portions 101b, 102b . In particular, the internal portions 101b, 102b are configured to positively traction-couple to the respective terminal portions 91 , 92 . Therefore , when the internal portions 101b, 102b are subj ect to traction, they cooperate with the main body 73 , in particular with the respective terminal portions 91 , 92 , from which they cannot be extracted .

[0051] Preferably, the internal portions 101b, 102b are hookshaped and the intermediate portions 101c, 102c extend along the spring axis SA.

[0052] Conveniently, the first coupling element 101 is identical to , in particular has the same shape and dimension of , the second coupling element 102 .

[0053] The first coupling element 101 and the second coupling element 102 are composed of a shaped wire . Preferably, the diameter of such shaped wire is greater than the diameter of the wire of the main body 73 .

[0054] Conveniently, the first end 81 of the spring 72 comprises a third coupling element 103 configured to hook to the first arm 21 , in particular to the first ring 41 , and the second 104 configured to hook to the second arm 22 , in particular to the second ring 42 .

[0055] In particular ( Figure 6 ) , the third coupling element 103 comprises an external portion 103a identical to the external portion 101a of the first coupling element 101 and arranged symmetrically thereto with respect to the spring axis SA, and the fourth coupling element 104 comprises an external portion 104a identical to the external portion 102a of the second coupling element 102 and arranged symmetrically thereto with respect to the spring axis SA.

[0056] The external portion 101a of the first coupling element 101 and the external portion 103a of the third coupling element 103 are open on opposite sides with respect to the spring axis SA. S imilarly, the external portion 102a of the second coupling element 102 and the external portion 104a of the fourth coupling element 104 are open on opposite sides with respect to the spring axis SA.

[0057] The external portion 103a of the third coupling element

[0058] 103 is configured to hook to the pin 111 of the first arm 21 and the external portion 104a of the fourth coupling element

[0059] 104 is configured to hook to the pin 112 of the second arm 22 .

[0060] In particular ( Figure 5 ) , the external portion 101a of the first coupling element 101 and the external portion 103a of the third coupling element 103 j ointly define a closed structure , like an eyelet , which winds the pin 111 of the first arm 21 . Similarly, the external portion 102a of the second coupling element 102 and the external portion 104a of the fourth coupling element 104 j ointly define a closed structure , like an eyelet , which winds the pin 112 of the second arm 22 .

[0061] Conveniently, the third coupling element 103 is identical to , in particular has the same shape and dimension of , the first coupling element 101 . Similarly, the fourth coupling element 104 is identical to , in particular has the same shape and dimension of , the second coupling element 102 .

[0062] The tubular appendage 64 of the second ring 42 ( Figure 4 ) is arranged inside a recess 131 obtained on a periphery of the first ring 41 for the purpose of limiting the relative rotation between the rings 41 , 42 between a free arm position corresponding to the minimum longitudinal expansion of the spring 72 and a load stop position corresponding to a maximum traction position of the spring 72 .

[0063] The spring 72 , in the absence of reaction forces from the belt 8 , tends to keep the rings 41 , 42 in the free arm position . For the purpose of allowing an easy mounting of the belt 8 , prior to the installation the rings 41 , 42 are locked with respect to one another in a relative angular installation position by a locking pin 132 which engages respective holes 141 , 142 thereof . The installation position is conveniently near the load stop position .

[0064] Once the belt 8 has been installed, the pin 132 is removed and, under the action of the spring 72 , the tensioner is brought into the nominal position schematically illustrated in Figure 2 , wherein the two pulleys 31 , 32 are located in a symmetrical position with respect to the bisecting line H of the wrap angle 0 of the belt 8 on the pulley 5 , coincident with the direction of the resultant of the pull of the belt 8 on the pulley 5 in nominal conditions .

[0065] The operation of the tensioner 11 is the following . In normal operating conditions , the engine 2 supplies drive torque and the electrical machine 7 is driven and operates as alternator . In this condition, the span 8a of the belt 8 is the taut span and the span 8b is the slack span .

[0066] With respect to the nominal position illustrated in Figure 2 , the tensioner 11 rotates clockwise about the axis Al by ef fect of the hubload transmitted from the taut span 8a to the pulley 31 . Under the thrust of the spring 72 , tending to bring the pulleys 31 and 32 close to one another, the pulley 32 acts on the slack span 8b keeping therein a predetermined minimum tension value as the torque varies .

[0067] In boost mode , the electrical machine 7 supplies driving power (positive torque ) which adds to that of the engine 2 . This tends to reduce the tension in the span 8a and to increase the tension in the span 8b of the belt 8 . Conversely, in recovery mode , the electrical machine 7 absorbs mechanical power (negative torque ) , and thus the tension in the span 8b of the belt 8 tends to decrease .

[0068] Conveniently, the use of an axis of rotation A2 of the second ring 42 distinct from the axis Al of the first ring 41 ( coincident in use , as mentioned, with the axis MA of the electrical machine 7 ) allows to obtain a reduction in the installation tension of the belt 8 with the same torque transmission capability in the slack span (understood as the span from time to time slack depending on the operating conditions ) .

[0069] Upon examination of the characteri stics of the tensioner 11 , the advantages of the present invention are evident .

[0070] In particular, since the first end 81 and the second end 82 are distinct from one another and from the main body 73 , the risk of deterioration or even breakage is drastically reduced, both during the installation of the belt and in use .

[0071] Finally, it is clear that modi fications and variations can be made to the tensioner 11 without going beyond the scope of protection defined by the claims .

[0072] For example , the first axis Al and the second axis A2 may be coincident with one another . In such a case , the first ring 41 and the second ring 42 are rotatable with respect to the base 12 about a common axis .

[0073] The base 12 may be fixed to the engine 2 instead of the casing 13 of the electrical machine 7 .

[0074] The first arm 21 and the second arm 22 may be substantially rod-shaped instead of ring-shaped . In such a case , the first arm 21 and the second arm 22 may be hinged to the base 12 about respective axes , distinct from or coincident with one another , or one of the first arm 21 and the second arm 22 may be hinged to the base 12 and carry, hinged to it , the other of the f irst arm 21 and the second arm 22 .

[0075] The external portions 101a, 102a may be eyelet-shaped .

[0076] The internal portions 101b, 102b may be eyelet-shaped or sphere-shaped or hemisphere-shaped .

Claims

CLAIMS1. Tensioner for an accessory drive of an internal combustion engine (2) , the accessory drive (1) comprising at least a first pulley (3) connected to a drive shaft (4) of the engine (2) , at least a second pulley (5) connected to an electrical machine (7) , and a belt (8) wound at least on the first pulley (3) and the second pulley (5) , the tensioner (11) comprising:- a base (12) configured to be fixed to one of the engine (2) and a casing (13) of the electrical machine (7) ;- a first arm (21) rotatable with respect to the base (12) about a first axis (Al) ;- a second arm (22) rotatable with respect to the base (12) about a second axis (A2) ;- a first tensioning pulley (31) carried by the first arm (21) and rotatable with respect to it about its own axis ( PAI ) ;- a second tensioning pulley (32) carried by the second arm (22) and rotatable with respect to it about its own axis (PA2) ; and- elastic means (71) acting on the first arm (21) and on the second arm (22) to push the first tensioning pulley (31) and the second tensioning pulley (32) into contact with respective spans (8a, 8b) of the belt (8) , the elastic means (71) comprising a traction spring (72) comprising a main body (73) extending along a spring axis (SA) , a first end (81) operatively interposed between the main body (73) and the first arm (21) , a second end (82) operatively interposed between the main body (73) and the second arm (22) , wherein the main body (73) , the first end (81) and thesecond end (82) are distinct elements.

2. Tensioner as claimed in claim 1, wherein the main body (73) is a helical spring made from a wire having a constant diameter.

3. Tensioner as claimed in claim 1 or 2, wherein the main body (73) comprises a first terminal portion (91) configured to cooperate with the first end (81) , a second terminal portion (92) configured to cooperate with the second end (82) , and a central portion (93) interposed between the first terminal portion (91) and the second terminal portion (92) .

4. Tensioner as claimed in claim 3, wherein the central portion (93) is a cylindrical helix.

5. Tensioner as claimed in claim 3 or 4, wherein the first terminal portion (91) is tapered and the second terminal portion (92) is tapered.

6. Tensioner as claimed in any of the preceding claims, wherein the first end (81) comprises a first coupling element (101) configured to hook to the first arm (21) and the second end (82) comprises a second coupling element (102) configured to hook to the second arm (22) .

7. Tensioner as claimed in claim 6, wherein the first arm (21) and the second arm (22) comprise respective pins (111, 112) , the first coupling element (101) and the second coupling element (102) comprising respective external portions (101a, 102a) , arranged externally to the main body (73) , hook-shaped and configured to hook to the respective pins (111, 112) .

8. Tensioner as claimed in claim 7, wherein the first coupling element (101) and the second coupling element (102) comprise respective internal portions (101b, 102b) , arrangedinternally to the main body (73) and configured to positively couple to the respective terminal portions (91, 92) , and respective intermediate portions (101c, 102c) interposed between the respective external portions (101a, 102a) and the respective internal portions (101b, 102b) .

9. Tensioner as claimed in claim 8, wherein the internal portions (101b, 102b) are hook-shaped and the intermediate portions (101c, 102c) extend along the spring axis (SA) .

10. Tensioner as claimed in any of claims 6 to 9, wherein the first coupling element (101) is identical to the second coupling element (102) .

11. Tensioner as claimed in any of claims 6 to 10, wherein the first coupling element (101) and the second coupling element (102) comprise a shaped wire.

12. Tensioner as claimed in any of claims 6 to 11, wherein the first end (81) comprises a third coupling element (103) configured to hook to the first arm (21) and the second end (82) comprises a fourth coupling element (104) configured to hook to the second arm (22) , the third coupling element (103) comprising an external portion (103a) identical to the external portion (101a) of the first coupling element (101) and arranged symmetrically thereto with respect to the spring axis (SA) , the fourth coupling element (104) comprising an external portion (104a) identical to the external portion (102a) of the second coupling element (102) and arranged symmetrically thereto with respect to the spring axis (SA) .

13. Tensioner as claimed in claim 12, wherein the third coupling element (103) is identical to the first coupling element (101) , and the fourth coupling element (104) is identical to the second coupling element (102) .

14. Tensioner as claimed in any of the preceding claims, wherein the second axis (A2) is coincident with the first axis (Al ) .

15. Tensioner as claimed in any of claims 1 to 13, wherein the first arm (21) and the second arm (22) comprise, respectively, a first ring (41) and a second ring (42) , the second axis (A2) being distinct from the first axis (Al) .

16. Accessory drive for an internal combustion engine (2) , comprising at least a first pulley (3) connected to a drive shaft (4) of the engine (2) , at least a second pulley (5) connected to an electrical machine (7) , a belt (8) wound at least on the first pulley (3) and the second pulley (5) , and a tensioner (11) as claimed in any of the preceding claims .

Images