GB2579586A

GB2579586A - Tensioning of belt drives

Info

Publication number: GB2579586A
Application number: GB1819797.0A
Authority: GB
Inventors: Scott Jonathan
Original assignee: Perkins Engines Co Ltd
Current assignee: Perkins Engines Co Ltd
Priority date: 2018-12-04
Filing date: 2018-12-04
Publication date: 2020-07-01
Also published as: GB201819797D0

Abstract

A belt drive (1) comprises a first pulley (4) and at least one additional pulley (5. 6) and uses an elastic belt (2) that is engagable over the pulleys (4, 5, 6). An auxiliary unit (3), connected to the first pulley (4), has a detent (20) that is moveable along a slot (13) of a tensioning link (10) as the auxiliary unit (3) is rotated between an operating position and a belt changing position. The slot (13) of the tensioning link (10) has a first portion (14) and a second portion (15) wherein in an operating position the detent (20) is locatable at a second end (43) of the second portion (15) of the slot and to obtain a belt changing position the detent (20) is movable to a first end (40) of the first portion (14) of the slot via a first end (42) of the second portion (15) of the slot and a second end (41) of the first portion (14) of the slot.

Description

Tensioning of Belt Drives

Technical Field

The disclosure relates to the tensioning of belt drives. For example, the tensioning of belt drives coupled to an internal combustion engine.

Background

A belt drive may be used to transfer rotary motion from a first element to a second element. For example, a belt drive may transfer rotary motion of a first pulley to a second pulley. The first pulley may be driven to rotate by an external driver, for example an internal combustion engine. The second pulley may be driven to rotate by frictional engagement of a belt that extends around the first pulley and the second pulley.

In some examples of belt drive a third pulley is provided and the belt extends around the first pulley, the second pulley and the third pulley. The belt may be a Multi-V-belt which takes is name from the shape adopted by the belt at each pulley.

For the belt drive to function correctly the belt must be tensioned correctly around the pulleys. If the belt is too loose then slippage will occur between the belt and the pulleys. If the belt is too tight then the useful life of the belt and or the bearings of the belt drive may be reduced.

Obtaining the correct tension of the belt may be achieved by choosing a specific length for the belt that matches a known geometry of the pulleys and their relative spacing. However, mounting of the belt may require the use of specialised assembly tooling or the use of multi-part pulleys that can be partially dissembled to allow the belt to be passed over the rims of the pulleys. Where the belt is an elastic belt it may be possible to stretch the belt sufficiently for it to pass over the rims of the pulleys. However, stretching of an elastic belt in this way may overstretch and damage the belt. It may also be difficult to reliably obtain the correct tension in the belt once it has been stretched over the rims of the pulleys.

DE 10 2004 006 577 Al discloses a belt drive for an alternator of an internal combustion engine of a motor vehicle. An elastic belt connects the internal combustion engine and the alternator drivingly to one another. At least one component of the alternator to which the elastic belt is applied is mounted with a changeable position. The component of changeable position permits the belt to be laid loosely over all the components of the belt drive to which it is applied and subsequently, by means of a change of position of the aforementioned component, to bring about a tensioning of the elastic belt in an operationally ready state. The alternator is rotatably mounted and provided with a stud bolt that passes through a parabolic slot in a slotted link member. The elastic belt is tensioned by rotating the alternator to move the stud bolt along the parabolic slot. A nut associated with the stud bolt is then tightened to lastingly ensure the operating position of the alternator.

While the arrangement of DE 10 2004 006 577 Al may permit tensioning of an elastic belt without the need for specialised assembly tooling or use of multi-part pulleys it still has disadvantages. First, the arrangement requires the use of a nut associated with the stud bolt to lastingly ensure the operating position of the alternator. Secondly, the arrangement does not ensure that a pre-defined tension in the elastic belt is obtained since the stud bolt can be fixedly located at a plurality of locations along the parabolic slot.

Summary of the disclosure

The present disclosure provides a belt drive comprising: a first pulley; at least one additional pulley; an elastic belt that is engagable over the first pulley and the at least one additional pulley; and an auxiliary unit connected to the first pulley; the auxiliary unit comprising a detent; the auxiliary unit being rotatable about a first pivot between an operating position and a belt changing position, wherein in the belt changing position the first pulley is closer to the at least one additional pulley than in the operating position such that a tension of the elastic belt is less in the belt changing position than in the operating position; the belt drive further comprising a tensioning link; the tensioning link comprising an elongate body having a slot receiving in a slidable manner the detent; the tensioning link being rotatable about a second pivot; the slot comprising a first portion extending along the elongate body and a second portion extending across the elongate body; the first portion of the slot having a first end proximal the second pivot and a second end distal the second pivot; the second portion of the slot having a first end proximal the first portion of the slot and a second end distal the first portion of the slot; the second end of the first portion of the slot opening into the first end of the second portion of the slot; the second end of the second portion being closer to the second pivot than the first end of the second potion; wherein in the operating position the detent is locatable at the second end of the second portion of the slot and to obtain the belt changing position the detent is movable to the first end of the first portion of the slot via the first end of the second portion of the slot and the second end of the first portion of the slot while rotating the auxiliary unit about the first pivot.

The present disclosure further provides a tensioning link for a belt drive comprising: an elongate body having an aperture for rotatably mounting the tensioning link to a pivot and a slot for receiving in a slidable manner a detent; the slot comprising a first portion extending along the elongate body and a second portion extending across the elongate body; the first portion of the slot having a first end proximal the aperture and a second end distal the aperture; the second portion of the slot having a first end proximal the first portion of the slot and a second end distal the first portion of the slot; the second end of the first portion of the slot opening into the first end of the second portion of the slot; the second end of the second portion being closer to the aperture than the first end of the second potion.

Brief description of the drawings

Specific embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a belt drive according to the present disclosure in an operating position; Figure 2 shows an enlarged view of a portion of Figure 1; Figure 3 shows the belt drive of Figure 1 in a belt changing position with an elastic belt omitted; and Figure 4 shows a tensioning link of the belt drive of Figure 1.

Detailed description

In the following description terms such as 'upper' and 'lower' are used to describe relative positions of features. Such terms are to be understood, unless the immediate context requires otherwise, as referring to an absolute frame of reference in which the force of gravity acts in a 'down' direction towards 'ground level'. As such, the terms 'upper' and lower' refer to relative positions from the ground level.

In the following description a part may be described as comprising a 'pivot'. For example, a first part may be described as comprising a pivot for rotatably coupling the first part to a second part. Unless the immediate context requires otherwise, the term pivot encompasses any suitable construction allowing rotational coupling of the first part to the second part. As non-limiting examples, the pivot may comprise a pin, shaft or axle that rotates within an aperture, casing or bearing. The pivot or a part of the pivot may be integral with the first part or integral with the second part. The pivot may comprise one or more additional components that couple between the first part and the second part.

As illustrated in Figures 1 to 4 there is provided a belt drive 1 comprising a first pulley 4, at least one additional pulley 5, 6, an elastic belt 2 and an auxiliary unit 3 connected to the first pulley 4. The elastic belt is engagable over the first pulley 4 and the at least one additional pulley 5, 6.

The belt drive 1 may be coupled to an internal combustion engine (ICE). The ICE may be part of a vehicle. The at least one additional pulley 5, 6 may include a driven pulley that is driven to rotate by an output of the ICE. The first pulley 4 is preferably driven to rotate by frictional engagement of the first pulley 4 with the elastic belt 2 as the elastic belt 2 moves over the first pulley 4.

In some embodiments the at least one additional pulley includes at least a second pulley 5 and a third pulley 6. In some embodiments the elastic belt 2 is an elastic Multi-V-belt and the first pulley 4, second pulley 5 and the third pulley 6 are spaced in a triangular arrangement as shown in Figure 1. The first pulley 4 may have an axis of rotation 7. The second pulley 5 may have an axis of rotation 8. The third pulley 6 may have an axis of rotation 9. The axes of rotation 7, 8, 9 may be parallel to one another.

In some embodiments the auxiliary unit 3 may be an alternator and rotation of the first pulley 4 may drive the alternator to generate electrical energy. The electrical energy may be supplied to a component of the ICE and or to a component of the vehicle.

The auxiliary unit 3 may comprise a housing 19, a first pivot 26 and a detent 20. The first pulley 4 may be coupled to the housing 19. The first pivot 26 may be provided at or near a lower extremity of the housing 19. The detent 20 may be provided at or near an upper extremity of the housing 19. In one example the detent 20 may be a stud bolt. The first pulley 4 may be coupled at or near a centre of the housing 19.

The first pivot 26 may rotatably mount the auxiliary unit 3 to an auxiliary unit mount 25 as shown in Figure 1. The auxiliary unit mount 25 may form a part of the ICE or vehicle or may itself be mounted to the ICE or vehicle.

The auxiliary unit 3 is rotatable about the first pivot 26 between an operating position (shown in Figures 1 and 2) and a belt changing position as will be discussed further below.

The belt drive further comprises a tensioning link 10, an example of which is shown in Figure 4. The tensioning link 10 comprises an elongate body 11 having a slot 13 receiving in a slidable manner the detent 20. The tensioning link 10 is rotatable about a second pivot 18. An aperture 12 may be provided in the elongate body 11 to permit mounting of the tensioning link 10 to form the second pivot 18. The second pivot 18 may rotatably mount the tensioning link 10 to a component (not shown for clarity) of the ICE or vehicle.

The elongate body 11 may be planar. The elongate body 11 may be formed from a sheet material, for example steel plate. The size of the elongate body 11 may be chosen dependent on the geometry of the belt drive. In some embodiments the elongate body 11 may have a length of 100 and 110 mm. Additionally or alternatively, the elongate body 11 may have a width of between 20 and 35 mm. Additionally or alternatively, the width may increase from a first end nearest the aperture 12 to a second end furthest from the aperture 12. The width at the first end may be between 20 and 25 mm. The width at the second end may be between 30 and 35 mm. Additionally or alternatively, the elongate body 11 may have a thickness of between 5 and 10 mm, for example 6 mm.

The slot 13 may have an internal width sufficient to allow the detent 20 to pass there through. In some embodiments the width is between 8 and 10 mm.

The slot 13 comprises a first portion 14 extending along the elongate body 11 and a second portion 15 extending across the elongate body 11. The first portion 14 of the slot 13 has a first end 40 proximal the aperture 12 (and thus also the second pivot 18) and a second end 41 distal the aperture 12. The second portion 15 of the slot 13 has a first end 42 proximal the first portion 14 of the slot 13 and a second end 43 distal the first portion 14 of the slot 13. The second end 41 of the first portion 14 of the slot 13 opens into the first end 42 of the second portion 15 of the slot 13. The second end 43 of the second portion 15 is closer to the aperture 12 than the first end 42 of the second potion 15.

The second end 41 of the first portion 14 of the slot 13 and the first end 42 of the second portion 15 of the slot 13 may meet at a slot apex 22. The slot 13 at the slot apex 22 may comprise a sharp internal corner 27 as shown in Figure 4.

The first portion 14 may have an end stop 31 at the first end 40 that is distal the slot apex 22. The end stop 31 may be formed by a closed end of the slot 13. The second portion 15 may have an end stop 30 at the second end 43 that is distal the slot apex 22. The end stop 30 may be formed by a closed end of the slot 13.

The first portion 14 of the slot 13 may be a longitudinal portion that may extend longitudinally along the elongate body 11. The second portion 15 of the slot 13 may be a transverse portion that may extend transversely across the elongate body 11.

The second portion 15 of the slot 13 may have a first edge 45 and a second edge 46 that extend between the first end 42 of the second portion 15 and the second end 43 of the second portion 15. The first edge 45 may be proximal the aperture 12. The second edge 46 may be distal the aperture 12. The first edge 45 may be orientated at an angle of 80 to 85° to a first radial line 24 passing from the aperture 12 through the second end 43 of the second portion 15 of the slot 13 as shown in Figure 4. The second edge 46 may be parallel to the first edge 45.

The second portion 15 may be straight. The first portion 14 may be straight. The first portion 14 may have an axis of extension 16. The second portion 15 may have an axis of extension 17. The first portion 14 may be longer than the second portion 15.

The first portion 14 may extend coincident with, or parallel to, a second radial line 28 which extends from the aperture 12. For example, the axis of extension 16 of the first portion 14 may be coincident with the second radial line 28. However, alternatively and preferably, as illustrated by way of example in Figure 4 the axis of extension 16 may be parallel to, and offset from, the second radial direction 28.

A distance between the aperture 12 and the second end 43 of the second portion 15 of the slot 13 may be configured to apply a predefined tension to the elastic belt 2 in the operating position.

In use, the tensioning link 10 is mounted rotatably about second pivot 18 using the aperture 12. The belt drive 1 may adopt its operating position as shown in Figure 1. In the operating position the detent 20 may be located at the end stop 30 at the second end 43 of the second portion 15 distal the slot apex 22. This position is shown in Figure 4 as position 20a. A distance between the second pivot 18 and the second end 43 of the second portion 15 may be configured to apply a predefined tension to the elastic belt 2 in the operating position. This distance is fixed by the fixed dimensions of the tensioning link 10 (and its slot 13). Further, since the position of the second pivot 18 is fixed relative to the axes of rotation 7, 8, 9 of the first pulley 4, second pulley 5 and third pulley 6, the predefined distance between the second pivot 18 and the second end 43 of the second portion 15 ensures that the tension of the elastic belt 2 may be predefined for when the auxiliary unit is in its operating position with the detent 20 at position 20a.

The first edge 45 of the second portion 15 may be angled such that, in the operating position, the tension in the elastic belt 2 urges the detent 20 against the end stop 30 at the second end 43 of the second portion 15 into position 20a such that the detent 20 is retained in the second portion 15 without requiring any additional securing means.

To obtain the belt changing position of the belt drive 1 the detent 20 may be moved into the first portion 14 past the slot apex 22 while rotating the auxiliary unit 3 about the first pivot 26. To move the detent 20 from the second portion 15, past the slot apex 22 and into the first portion 14 it may be required to first rotate to auxiliary unit 3 in a first sense (clockwise as viewed in Figure 1) that increases a tension in the elastic belt 2 before rotating the auxiliary unit 3 in an opposite, second sense (anti-clockwise as viewed in Figure 1) that decreases the tension in the elastic belt 2. The angling of the first edge 45 of the second portion 15 may be chosen such that the degree of increase in the tension of the elastic belt 2 is kept small to prevent over-stretching of the elastic belt 2.

As the auxiliary unit 3 is rotated in the first sense the tensioning link 10 may be manually lifted in the direction A shown in Figure 2 to assist in moving the detent 20 along the second portion 15. The position of the detent 20 as it passes the slot apex 22 is shown in Figure 3 as position 20b. Once past the slot apex 22 the detent 20 is free to slide along the first portion 14 towards the end stop 31 at the first end 40 into the location marked as position 20c in Figure 3.

In the belt changing position the auxiliary unit 3 has been rotated such that the first pulley 4 is now closer to the at least one additional pulley 5, 6 than in the operating position as shown in Figure 3 such that a tension of the elastic belt 2 is less in the belt changing position than in the operating position. Thus, in the belt changing position the elastic belt 2 may more easily be mounted and dismounted from the pulleys 4, 5, 6. Figure 3 shows the belt drive 1 with the elastic belt 2 removed.

To return the belt drive 1 to its operating position the above steps may be reversed. In particular, rotating the auxiliary unit 3 in the first sense (clockwise as viewed in Figure 1) slides the detent 20 along the first portion 14 from position 20c to position 20b. At this point the tensioning link 10 may have a tendency to drop under gravity to move the detent 20 into the second portion 15. This movement may be assisted manually. As the auxiliary unit 3 is released the tension in the elastic belt 2 will urge the detent 20 to slide along the second portion into engagement with the end stop 30 at position 20a.

Industrial Applicability

The present disclosure finds application in providing a tensioning link and a belt drive that may be used, for example, with internal combustion engines. In one example, the auxiliary unit may be an alternator.

The present disclosure may find particular application where the elastic belt is an elastic Multi-V-belt.

Advantageously, the belt drive of the present disclosure may produce a pre-defined tension in the elastic belt without requiring use of a fixative, for example a nut, that is applied between the tensioning link and the detent of the auxiliary unit. This may allow a simplified arrangement which is easier to install and operate. In particular, the movement of the auxiliary unit between its operating position and its belt changing position may be achieved without the use of any tools, i.e. in a tool-free operation.

Advantageously, the belt drive of the present disclosure may ensure that a pre-defined tension in the elastic belt is always obtained since the detent of the auxiliary unit will always be urged against the end stop of the second portion distal the slot apex of the slot when the auxiliary unit is in its operating position.

Advantageously, there may be no risk that the detent is fixed in an alternative location of the slot that is not the end stop of the second portion. In other words, the design of the tensioning link may ensure that there is only one possible location for the detent when the auxiliary unit is in its operating position.

Advantageously, the angling of the second portion of the slot relative to the first portion of the slot may ensure that the tensioning link is 'self-locking' when the auxiliary unit is in its operating position without the need for any additional fixing. In particular, when the auxiliary unit is in its operating position the tension in the elastic belt always urges the detent against the end stop of the second portion of the slot. However, optionally an additional fixing may be applied to the detent to provide an additional resistance against movement of the detent within the slot. For example, a nut may be applied to the detent in the example where the detent is a stud bolt.

Claims

-10 -CLAIMS: 1. A belt drive comprising: a first pulley; at least one additional pulley; an elastic belt that is engagable over the first pulley and the at least one additional pulley; and an auxiliary unit connected to the first pulley; the auxiliary unit comprising a detent; the auxiliary unit being rotatable about a first pivot between an operating position and a belt changing position, wherein in the belt changing position the first pulley is closer to the at least one additional pulley than in the operating position such that a tension of the elastic belt is less in the belt changing position than in the operating position; the belt drive further comprising a tensioning link; the tensioning link comprising an elongate body having a slot receiving in a slidable manner the detent; the tensioning link being rotatable about a second pivot; the slot comprising a first portion extending along the elongate body and a second portion extending across the elongate body; the first portion of the slot having a first end proximal the second pivot and a second end distal the second pivot; the second portion of the slot having a first end proximal the first portion of the slot and a second end distal the first portion of the slot; the second end of the first portion of the slot opening into the first end of the second portion of the slot; the second end of the second portion being closer to the second pivot than the first end of the second potion; wherein in the operating position the detent is locatable at the second end of the second portion of the slot and to obtain the belt changing position the detent is movable to the first end of the first portion of the slot via the first end of the second portion of the slot and the second end of the first portion of the slot while rotating the auxiliary unit about the first pivot.
2. The belt drive of claim 1, wherein the second end of the first portion of the slot and the first end of the second portion of the slot meet at a slot apex.
3. The belt drive of claim 1 or claim 2, wherein the first portion of the slot extends longitudinally along the elongate body and the second portion of the slot extends transversely across the elongate body.
4. The belt drive of any preceding claim, wherein the second portion of the slot comprises a first edge that extends between the first end of the second portion and the second end of the second portion; the first edge being proximal the second pivot; wherein the first edge is orientated at an angle of 80 to 85° to a radial line passing from the second pivot through the second end of the second portion of the slot.
5. The belt drive of any preceding claim, wherein the second portion is straight.
6. The belt drive of any preceding claim, wherein the first portion extends in, or parallel to, a radial line extending from the second pivot.
7. The belt drive of any preceding claim, wherein a distance between the second pivot and the second end of the second portion of the slot is configured to apply a predefined tension to the elastic belt in the operating position.
8. The belt drive of any preceding claim, wherein the second portion is angled such that, in the operating position, a tension in the elastic belt urges the detent against an end stop of the second portion such that the detent is retained in the second portion without requiring any additional securing means.
9. The belt drive of any preceding claim, wherein the angling of the first portion and the second portion is such that to move the detent from the second end of the second portion of the slot to the first end of the first portion of the slot, requires the auxiliary unit to first be rotated in a first sense that increases a tension in the elastic belt before being rotated in an opposite, second sense that decreases the tension in the elastic belt.
10. The belt drive of any preceding claim, wherein the auxiliary unit is an alternator.
11. The belt drive of any preceding claim, wherein the at least one additional pulley comprises a second pulley and a third pulley and wherein the elastic belt is an elastic Multi-V-belt.
-12 - 12. A tensioning link for a belt drive comprising: an elongate body having an aperture for rotatably mounting the tensioning link to a pivot and a slot for receiving in a slidable manner a detent; the slot comprising a first portion extending along the elongate body and a second portion extending across the elongate body; the first portion of the slot having a first end proximal the aperture and a second end distal the aperture; the second portion of the slot having a first end proximal the first portion of the slot and a second end distal the first portion of the slot; the second end of the first portion of the slot opening into the first end of the second portion of the slot; the second end of the second portion being closer to the aperture than the first end of the second potion.
13. The tensioning link of claim 12, wherein the second end of the first portion of the slot and the first end of the second portion of the slot meet at a slot apex.
14. The tensioning link of claim 12 or claim 13, wherein the first portion of the slot extends longitudinally along the elongate body and the second portion of the slot extends transversely across the elongate body.
15. The tensioning link of any one of claims 12 to 14, wherein the second portion of the slot comprises a first edge that extends between the first end of the second portion and the second end of the second portion; the first edge being proximal the aperture; wherein the first edge is orientated at an angle of 80 to 85° to a radial line passing from the aperture through the second end of the second portion of the slot.
16. The tensioning link of any one of claims 12 to 15, wherein the second portion is straight.
17. The tensioning link of any one of claims 12 to 16, wherein the first portion extends in, or parallel to, a radial line extending from the aperture.