Patent Application
20200386302
This application claims priority to German Application No. DE 10 2019 115 628.9, filed on Jun. 7, 2019, which application is hereby incorporated herein by reference in its entirety.
A traction drive usually comprises an endless traction means and at least two drive pulleys, one of which can act as the drive and one as the output of the traction drive. Such traction drives are used, for example, on internal combustion engines of a motor vehicle to drive auxiliary units, a first drive pulley being located on the crankshaft of the internal combustion engine and driving the traction means. Other drive pulleys are assigned to the auxiliary units, such as water pump, alternator or air conditioning compressor, and are rotatingly driven by the traction drive. In conventional traction drives, the auxiliary units are designed as consumers, i.e. they are driven by the drive pulley of the crankshaft via the traction means. In this case, an undriven portion (slack side) of the traction means is formed between the crankshaft and the unit adjoining the crankshaft in circumferential direction of the traction means, said adjoining unit typically being a generator. To ensure a sufficient wrap of the traction means around the drive pulley, the traction means is pretensioned by a tensioning roller of the tensioning arrangement.
Depending on the arrangement of the auxiliary units present in such a traction drive (generator, water pump, air-conditioning compressor), a traction drive can react more or less sensitively to a defective position on a drive pulley. This applies in particular to the drive pulley in the run before entering a generator. This can lead to an undesired axial running behaviour of the traction means, which can have negative effects such as wear of the traction means or noise.
From DE 10 2011 088 213 A1 a tensioning arrangement for a traction drive of a power unit of an internal combustion engine is known. The tensioning arrangement comprises several pulleys drivingly connected via a traction means, one of which being connected to an auxiliary unit of the internal combustion engine. Two tensioning elements are arranged on both sides of the pulley connected to the unit, which are mounted on a common lever. The tensioning elements are each pretensioned against the traction means via the lever by means of a tensioning unit. In order to prevent excessive stressing of the traction means by axial movement, which can occur due to misalignment between the tensioning element and the pulley, a roller of the tensioning element guiding the traction means is designed spherical and mounted in the lever so that it can be tilted about a vertical axis or moved axially.
From WO 201 8/1 781 43 A1 a tensioning device for a traction drive is known. The tensioning device comprises a base member, a tensioning arm with a bearing carrier and a tensioning roller, which is mounted so as to be pivotable relative to the base member, and spring means for loading the tensioning arm. An adjusting device is provided for adjusting a spring support relative to the bearing carrier of the tensioning roller.
From DE 10 2015 111 809 A1 a tensioning device for a traction means is known, which comprises a receiving housing, a roller carrier with a tensioning roller, a bearing arrangement with which the roller carrier is mounted in the receiving housing so as to be rotatable about an axis of rotation, and a helical tension spring which is supported on the receiving housing and the roller carrier in the circumferential direction and in the axial direction respectively.
The present disclosure relates to a tensioning arrangement for a traction drive and to a device for adjusting a tensioning arrangement. The present disclosure describes a tensioning arrangement which allows a traction means to run well on the tensioner roller and with a long service life. The present disclosure further describes a corresponding adjusting device with which such a tensioning arrangement can be adjusted.
A tensioning arrangement for a traction drive comprises: a base member; at least one tensioning arm, which is pivotally mounted relative to the base member about a pivot axis; a tensioning roller, which is rotatably connected to a carrier element of the at least one tensioning arm by a bearing about an axis of rotation; and an adjustment mechanism configured to pivot the bearing relative to the carrier element in a pivoting range and to fix the bearing in a pivoted position within the pivoting range.
An advantage of the tensioning arrangement is that the bearing and, respectively, the tensioning roller rotatably mounted therewith can be adjusted relative to the carrier element and, respectively, the base member of the tensioning arrangement by means of the adjustment mechanism. Thus, a defined misalignment of the tensioning roller relative to the roller carrier and the base member, respectively, can be achieved in a simple and cost-effective manner, wherein the misalignment can also be zero. The defined alignment, respectively the defined misalignment, can be maintained within very narrow tolerances, so that a high positional accuracy of the tensioning roller relative to the traction means is achieved during operation of the tensioning arrangement. The defined alignment, respectively the defined misalignment, can also include a pre-tilting within the narrow tolerances.
The tensioning arrangement is used to tension a traction means of a traction drive; it can also be referred to as tensioner for short. The traction drive is designed to transmit torque between two or more shafts by means of the endless traction means. In particular, the traction drive can be designed as a belt drive, toothed belt drive or chain drive. Accordingly, the tensioning arrangement can be designed in the form of a belt tensioning arrangement or chain tensioning arrangement. The tensioning arrangement can also be referred to as tensioning assembly or tensioning device.
With the aid of the adjustment mechanism, the tensioning roller can be adjusted and fixed relative to the carrier element within a defined adjustment range. In particular, it is provided that the tensioning roller bearing is pivotable with its axis of rotation relative to a carrier axis (A12) of the carrier element within a limited pivoting range. The pivoting range or pivoting angle (a) by which the bearing of the tensioning roller, respectively its axis of rotation (A5), is pivotable relative to the carrier element, respectively a carrier axis (A12), for example amounts up to a maximum of ±1° (α=±) 1°. The carrier axis (A12) extends in particular parallel to the pivot axis (A4, A6) of the tensioning arm through the bearing center (C) of the tensioning roller bearing. By limiting the pivot angle range (a), an incorrect adjustment or failure when the adjustment mechanism is released can be prevented.
The adjustment mechanism can be designed in particular in such a way that the tensioning roller is pivotable at least in a pivoting plane (Ea) which, in axial view of the carrier axis (A12), lies within an angular range (β) of up to ±30° around the carrier axis (A12) relative to a tangent plane (T). The tangent plane (T) can be defined as a plane perpendicular to the radius (R) extending from the pivot axis (A4) to the carrier axis (A12) or to the bearing center (C). It goes without saying that the adjustment mechanism can also be designed in such a way that the axis of rotation (A5) relative to the carrier axis (A12)—in axial view of the carrier axis (A12)—can also be pivoted within larger angular ranges (6), in particular also in any pivoting direction around the carrier axis (A12), that is over 360° around the carrier axis.
In an example, the adjusting mechanism can comprise a bearing receptacle in which the bearing is received, a supporting element against which the bearing receptacle is axially supported, and a clamping element for clamping the bearing receptacle against the supporting element. When the clamping element is not tensioned, the bearing receptacle is pivotable relative to the supporting element so that the bearing and the tensioning roller, respectively, can be set to the desired position relative to the supporting element. Subsequent tensioning by means of the clamping element fixes the bearing receptacle and the tensioning roller mounted therein in the desired position relative to the supporting element and the roller carrier, respectively.
On the side facing the carrier element, the bearing receptacle can have a contact face which is in contact with a supporting face of the supporting element. The contact face of the bearing receptacle and/or the supporting face of the supporting element are designed in such a way that the bearing receptacle can be pivoted and brought into contact in various positions relative to the supporting element. In particular, at least one of the contact face and the supporting face can be spherical, with, for example, both surfaces being spherical. The supporting face can be concave, while the contact face can be convex.
On the side facing away from the carrier element, the bearing receptacle can have a pressure face that can be brought into contact with and/or acted upon by a clamping face of the clamping element. Here, too, the pressure face of the bearing receptacle and/or the clamping face of the clamping element is designed in such a way that the bearing receptacle can be pivoted in various positions relative to the clamping element and can be loaded by same. In particular, at least one of the pressure face and the clamping face can be spherical, whereby both surfaces can be spherical.
In an example, the bearing can be pivoted relative to the carrier element about a pivot point that lies within the axial extension of the bearing. In this case the pressure face can be convex and the contact face can be concave. Furthermore, a radius of the spherical face (pressure face and/or contact face) can be smaller than a greatest outer radius of the tensioning roller, in particular smaller than a greatest outer radius of the bearing. In an example, the surface pairings are designed in such a way that overall a spherical structure of the bearing receptacle is obtained, wherein the centre of rotation resulting from the surface pairings can be located in the bearing centre plane.
In an example, the bearing can be pivoted relative to the carrier element about a pivot point that lies outside the axial extension of the bearing, in particular on a side opposite to the base member with respect to a bearing centre plane. In this case the pressure face can be concave and the contact face can be convex. Furthermore, a radius of the spherical face (pressure face and/or contact face) can be larger than a greatest outer radius of the bearing, in particular larger than a greatest outer radius of the tensioning roller. In an example, the surface pairings are designed in such a way that overall a double-spherical structure of the bearing receptacle is obtained, wherein the pivot point resulting from the surface pairings can be located with an axial offset to the tensioning roller.
In an example, the bearing receptacle can have a two-part design, with a first bearing receiving part that receives the bearing at a first axial end and a second bearing receiving part that receives the bearing at a second axial end. The first and the second bearing receiving part can be pivoted to a limited extent relative to the supporting element, and clamping element respectively, and can be axially clamped against each other in the desired pivot position by the clamping element. The bearing receptacle receives and holds the bearing and can thus also be referred to as bearing retainer, bearing holder or bearing seat.
The bearing receptacle can have a central bore through which the clamping element extends, with the clamping element having radial clearance relative to a bore wall. In a two-part design of the bearing receptacle, for example, both bearing receiving parts have a through bore through which the clamping element is inserted and clamped to the carrier element.
In particular, the clamping element is releasably clamped to the carrier element, for example by a bolted connection. For this purpose, one of the clamping element and the carrier element can comprise a bolt or screw with an outer thread, and the other of the clamping element and the carrier element can comprise a nut with an inner thread matching the bolt thread.
The tensioning arrangement can be designed as a single-arm or two-arm tensioning device. In a single-arm tensioner, exactly one tensioning arm is provided, which by spring means is resiliently supported in the circumferential direction against the base member. In this embodiment, one spring end is supported on the tensioning arm and the other spring end is supported on the base member in the circumferential direction, so that the tensioning arm can exert a resilient pretensioning force at a portion on the traction means when installed.
A two-arm tensioner has two tensioning arms, namely a first tensioning arm with a first tensioning roller and a second tensioning arm with a second tensioning roller, with the two tensioning arms being supported against each other in the circumferential direction by spring means. The first tensioning arm loads the traction means by the first tensioning roller. The second tensioning arm loads the traction means by the second tensioning roller. The two tensioning arms can be supported against each other and/or against the base member so as to be pivotable about their own or a common pivot axis. In this embodiment with two tensioning arms, a first spring end is supported in the circumferential direction on the first tensioning arm and a second spring end is supported on the second tensioning arm in the circumferential direction, so that the two tensioning arms are supported resiliently relative to each other in the circumferential direction via the spring means.
Two-arm tensioners are used in belt drives in which a starter generator is comprised in the belt drive as an auxiliary unit, i.e. an electric motor that can be operated as a starter (starter) or alternator (generator) depending on the operating mode. In normal or engine operation, the belt pulley on the crankshaft is the driving pulley, while the starter generator is driven like the other auxiliary units. In starting or starter mode, the starter generator drives the crankshaft via the associated pulley to start the combustion engine. In such belt drives with a starter generator as an auxiliary unit, between engine operation on the one hand and starter operation on the other hand, there is a change between the tight side and the slack side of the belt with respect to both sides of the pulley of the starter generator. It is therefore necessary to provide spring-loaded tensioning rollers for both of the said sides of the belt and thus two tensioning arms, one of which acts on the slack side under spring force, while the other is forced back by the tensioned side of the belt.
The present disclosure describes a device for adjusting a tensioning arrangement, which can be designed according to one or more of the above-mentioned embodiments, comprising: a base plate, a holding device for fixing the tensioning arrangement to the base plate, and an alignment element, which is connected to the base plate and has at least one alignment face against which the tensioning roller can be brought into contact in the tensioned state of the tensioning arrangement, such as a belt tensioner.
With this device, the tensioning roller can be easily adjusted to the desired position relative to the carrier element and the base member of the tensioning arrangement, respectively, and fixed in this position. At the beginning, the alignment element of the adjusting device can be adjusted once to the position required for the desired pivot position of the tensioning roller. By placing the tensioning arrangement on the holding device and making the tensioning roller contact against the alignment face under spring preload, the tensioning roller is pivoted into the desired position. By subsequently tensioning the tensioning roller on the carrier element, the arrangement is fixed in this position.
In an example, the alignment element has at least two alignment faces offset to each other in the circumferential direction of the tensioning roller. In this way a secure support in a plane parallel to the bearing axis is achieved. Alternatively or additionally, the alignment element can have at least two alignment faces that are offset to each other in the axial direction of the tensioning roller. In this way, a secure support in a plane parallel to the bearing axis is achieved.
The base member 3 can be attached to a stationary component such as an auxiliary unit. In principle, the auxiliary unit can be any machine which is part of the belt drive, i.e. in particular any of the auxiliary units driven by the main engine of the motor vehicle, such as the generator, water pump or the like. For connection to the stationary component, the base member 3 has fastening elements 46, which in particular can be configured as radially outwardly projecting flange projections with holes, through which screws for fastening to the stationary component may be inserted.
The two tensioning arms 4, 6 of the tensioning arrangement 2 are mounted so as to be rotatable about a pivot axis A4, A6 relative to each other, respectively relative to the base member 3 by means of appropriate bearing means. The base member 3, the first tensioning arm 4 and/or the second tensioning arm 6 can be manufactured as steel components, which in particular may be formed from sheet metal, or as light metal components, in particular from an aluminium casting alloy, or from plastic, in particular a fibre-reinforced plastic.
The first tensioning arm 4 is pivotably supported around a first pivot axis A4 by a first bearing. The second tensioning arm 6 is pivotably supported about a second pivot axis A6 by a second bearing. The two bearings are arranged coaxially, i.e. the two pivot axes A4 and A6 coincide. However, for certain embodiments it is also possible that the two pivot axes can be arranged parallel or eccentrically to each other.
The spring 8 extending circumferentially around the pivot axes A4, A6 counteracts a relative pivot movement of the two tensioning arms 4, 6. The two tensioning arms 4, 6 can be rotated relative to each other only to a limited extent due to the interposed spring 8 and, together with the spring 8, can rotate freely about the axes A4, A6 relative to the base member 3, i.e. by 360° and more. The pivot axes A4, A6 are arranged within the opening 47 of the base member 3 when the tensioning arrangement 2 is mounted.
The tensioning arms 4, 6 each have a carrier element 12, 13 which projects radially outwardly from an annular portion 14, 15 of the respective tensioning arm 4, 6. An associated tensioning roller 5, 7 is mounted to each carrier element 12, 13. The tensioning rollers 5, 7 are rotatably supported by respective bearings 16 about axes of rotation A5, A7 which are at least substantially parallel to the pivot axes A4, A6.
For example, at least one of the two tensioning arms 4, 6 is provided with an adjusting mechanism 11 in order to pivot the tensioning roller bearing 16 relative to the associated carrier element 12, 13 in a pivoting range and to fasten it in a pivoting position within the pivoting range. For this purpose, the tensioning roller bearing 16 can be pivoted with its axis of rotation A5, A7 relative to a carrier axis A12, A13 of the carrier element 12, 13 within a limited pivoting range a. The pivot range a is, for example, up to a maximum of ±1° (α±1°) about the axis A12, A13 of the carrier element, respectively about the pivot axis A4, A6 of the tensioning arm.
The adjusting mechanism 11 has a bearing receptacle 17 for the bearing 16, a supporting element 18 for supporting the bearing receptacle 17 in the direction of the carrier element 12, 13, and a tensioning element 19 for tensioning the bearing receptacle 17 against the supporting element 18, The bearing receptacle 17 can be pivoted and/or rotated relative to the supporting element 18 when the tensioning element 19 is released or not tensioned, so that the bearing 16 and the tensioning roller 5, 7 connected thereto can be adjusted to the desired position relative to the supporting element 18. By subsequently tensioning the arrangement by means of the tensioning element 19, the bearing receptacle 17 and the tensioning roller 5, 7 rotatably supported therein is fixed in the desired position relative to the supporting element 18 and the carrier element 12, 13, respectively.
In an example, the bearing receptacle 17 is designed in two parts and comprises a first bearing receiving part 17A, which receives a bearing inner ring 20 of the bearing 16 at a first axial end, and a second bearing receiving part 17B, which receives the bearing inner ring 20 at a second axial end. The first and second bearing receiving parts can also be referred to as bearing seat parts. In the unclamped state, the two bearing receiving parts 17A, 17B can be pivoted relative to the supporting element 18 and clamping element 19 respectively. In the desired pivot position of the tensioning roller 5, 7 relative to the respective carrier element 12, 13, the tensioning element 19 is braced against the supporting element 18 with the bearing receptacle 17 being interposed therebetween, so that the alignment of the tensioning roller is fixed. This adjustment position is maintained when operating the tensioning arrangement in a belt drive, so that the belt rests evenly on the adjusted tensioning roller and is guided securely.
The bearing receptacle 17 and the two receiving parts 17A, 17B have a central bore 21A, 21B, through which the clamping element 19 extends. As can be seen in particular in
On the side facing the carrier element 12, the bearing receptacle 17, more particularly the bearing receiving part 17A has a contact face 23 which is in contact with a support face 24 of the supporting element 18. The pair of faces formed by the contact face 23 and the supporting face 24 is designed in such a way that the bearing receiving part 17A can be pivoted into various positions relative to the supporting element 18 and brought into contact with same. For this purpose, the contact face 23 is in particular spherical or convex, and the supporting face 24 is in particular hollow-spherical or concave.
The bearing receiving part 17B on the side facing away from the carrier element 12 has a pressure face 25 which can be brought into contact with a clamping face 26 of the clamping element 19 and can be loaded by same. Here, too, the pair of faces formed by the pressure face 25 and the clamping face 26 is designed in such a way that the bearing seat 17B can be pivoted in various positions relative to the clamping element 19 and can be loaded by same. For this purpose, the pressure face 25 is designed in particular to be spherical or convex, and the clamping face 26 is designed in particular to be hollow-spherical or concave.
All in all, the spherical contact face 23 of the lower bearing receiving part 17A and the spherical pressure face 25 of the upper bearing receiving part 17B result in an overall spherical shape of the bearing retainer 17, so that a kind of ball joint is formed in cooperation with the supporting element 18 and the clamping element 19.
The pairs of faces 23, 24; 25, 26 in the present embodiment are designed in such a way that the bearing receptacle 17 can be pivoted about a pivot point M relative to part 22 and/or the carrier element 12. The pivot point M lies within the axial extension of the bearing 16, in particular in the bearing centre plane E. The radius R17 of the spherical outer faces 23, 25 of the bearing receptacle 17 and/or the spherical inner faces 24, 26 is smaller than a greatest outer radius R5 of the tensioning roller 5, in particular smaller than a maximum outer radius R16 of the bearing 16.
The clamping element 19 is designed in the form of a clamping screw or bolt which can be detachably clamped to part 22 supported against the carrier portion 12. Accordingly, the clamping element 19 has a head portion 27 for supporting against the bearing receptacle 17 and a threaded portion 28 for screwing to part 22. Part 22 has a sleeve portion with an internal thread 29 into which the clamping element is screwed with its external thread. The head portion 27 of the clamping element 19 comprises on its inside the clamping face 26 and on its outside an engagement contour for introducing a torque by means of a suitable tool. Furthermore, the clamping element 19 comprises a cylindrical portion 30 adjoining the head portion 27, which is positioned with radial clearance in the through bore 21B of the bearing receiving part 17B. The part 22 is axially supported by a head portion 31 against the carrier portion 12 of the tensioning arm. The supporting element 18 is annularly formed and is arranged coaxially around part 22. The supporting element 18 is axially braced by the clamping element 19 and part 22 between the bearing receptacle 17 and the carrier portion 12 of the tensioning arm.
Depending on the application and use of tensioner arrangement 2, only the first tensioning roller 5, or only the second tensioning roller 6, or both tensioning rollers 5, 6 can be equipped with an adjustment mechanism 11 as shown in
The only difference lies in the design of clamping element 19 and part 22, which are cinematically reversed in this case. The element 22 is designed in the form of a clamping bolt which is inserted through the tensioning arm 12 and is axially supported by a head portion 31. Accordingly, the clamping element 19 is designed in the form of a clamping nut which engages with an inner thread in an outer thread of the clamping bolt 22. The head portion 27 of the clamping nut 19 comprises the internal clamping face 26 for acting on the bearing receiving part 17B. On the outside, the clamping nut can have an engagement contour for introducing a torque by means of a suitable tool. As with the above-described embodiment, only one tensioning roller 5, 6, or both tensioning rollers 5, 6 can be equipped with the described adjustment mechanism 11 as shown in
A special feature is the design of the adjusting mechanism 11, which in the embodiment according to
The tensioning arrangement 2 according to the present embodiment has only one single tensioning arm 4 with corresponding tensioning roller 5. The first spring support is assigned to the single tensioning arm 4, as in the above embodiments. The second spring support is assigned to the base member 3 and/or is formed on same. The spring is arranged within the base member 3 and is not visible.
Another difference is that part 22, with which the clamping element 19 is clamped, is designed in one piece with the carrier element 12. For this purpose, the carrier element 12 of the tensioning arm 4 has a bore with an internal thread, into which the clamping element 19, designed as a clamping screw, is screwed. The tensioning arm 4 and carrier portion 12 respectively is designed as a solid part, for example as a light metal casting.
For all other details of design and operation, the tensioning arrangement 2 in
The tensioning roller 5 can be pivoted with its axis of rotation A5 relative to the carrier axis A12 of the carrier element 12, wherein the carrier axis A12 can be defined as parallel to the pivot axis A4 of the tensioning arm through the bearing centre C of the tensioning roller bearing 16. When the tensioning roller 5 is not pivoted, the axis of rotation (A5) and the carrier axis A12 coincide. In the pivoted state, the rotary axis and the carrier axis A12 define a pivot plane Ea. In the axial view shown, the pivot plane Ea can lie within an angular range 13 of up to ±180° around the carrier axis A12 relative to a tangent plane T. In particular, the tangent plane T is a plane perpendicular to the radius R, which extends from the pivot axis A4 to the bearing center C. In an example, the axis of rotation A5 in the axial view shown can be pivoted at least within an angular range 13 of up to ±30° relative to the tangent plane T. For example, the exact adjustment of the axis of rotation A5 can be oriented, depending on the specific design and installation situation, to the belt 34 wrapped around the tensioning roller 5. The pivot plane Ea can be located at least approximately in the bisecting plane between the two belt portions adjacent to the tensioning roller.
The adjusting device 40 comprises a base plate 41, a holding device 42 for fixing the tensioning arrangement 2 to the base plate 41, and an alignment element 43 which is connected to the base plate 41 and has a plurality of alignment faces 44, 45 against which the tensioning roller 7 can be brought into contact in a tensioned state of the belt tensioner 2.
The device 40 enables the tensioning roller 7 to be easily adjusted to the desired position relative to the carrier element 12 and the base member 3 of the tensioning arrangement 2 respectively and to be fixed in this position. The alignment element 43 of the adjusting device 40 is initially set in the position required for the desired pivot position of the tensioning roller 7 or is provided in the desired configuration. By placing the tensioning arrangement 2 on the holding device 42 and applying the tensioning roller 7 against the alignment faces 44, 45 under spring pretension, the tensioning roller 7 is pivoted into the desired position. The arrangement is fixed in this position by subsequently tensioning the tensioning roller 7 on the carrier element 12 by means of the tensioning element 19.
The alignment element 43 has at least two alignment faces 44, 44′ which are offset to each other in the circumferential direction of the tensioning roller 7. In this way a secure support is achieved in a plane perpendicular to the axis of rotation A5. Furthermore, the alignment element 43 has at least two alignment faces 44, 45′ which are offset to each other in the axial direction of the tensioning roller 7. In this way a secure support in a plane parallel to the axis of rotation A5 is achieved.
A special feature of the present embodiment according to
An advantage of the tensioning arrangements 2 and the adjusting devices 40 is that the bearings 16 of the tensioning rollers 5, 7 and accordingly the respective tensioning roller can be adjusted to a desired position relative to the carrier element 12, 13. A defined misalignment of the tensioning roller 5, 7 relative to the carrier 12, 13 and base member 3 respectively can be achieved in a simple and cost-effective manner, which can also be zero.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 115 628.9 | Jun 2019 | DE | national |
