GB2559143B

GB2559143B - Belt jump protection system

Info

Publication number: GB2559143B
Application number: GB1701290.7A
Authority: GB
Inventors: Duncombe Andrew; Beckett Richard
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-01-26
Filing date: 2017-01-26
Publication date: 2019-09-18
Anticipated expiration: 2037-01-26
Also published as: GB2559143A; DE112018000536T5; WO2018138040A1; GB201701290D0

Description

BELT JUMP PROTECTION SYSTEM

TECHNICAL FIELD

The present disclosure relates to a belt jump protection system and particularly, but not exclusively, to a belt jump protection system for an automotive internal combustion engine. Aspects of the invention relate to a belt drive system, to a belt integrated starter generator system, to an engine, to a vehicle, to a kit of parts for forming a belt drive system, and to a method of assembling a belt drive system.

BACKGROUND

Automotive vehicle engines are commonly provided with one or more auxiliary devices or engine accessories that are powered by a belt drive system. Examples of devices commonly powered by a belt drive system include alternators and generators, compressors and pumps. In some cases an engine may be provided with a belt integrated starter generator (BISG) that is configured to be driven by the belt drive system in a driven mode of operation and to drive the belt drive system in order to provide power to the engine in a powered mode of operation.

Automotive belt drive systems typically employ a ribbed belt with a plurality of longitudinal ribs that are configured to be received in corresponding plurality of grooves provided on the tracks of the accessory pulleys. As long as a ribbed belt is kept in tension the ribs of the belt and the corresponding grooves of the pulleys act to retain the belt on the pulleys such the belt is prevented from slipping axially along the pulleys or falling off the ends of the pulleys, as can happen with flat belts and toothed belts. For this reason it is not generally necessary to provide any additional features for preventing a ribbed belt from slipping off the pulleys, for example an integrated retaining flange which is sometimes included in a pulley for a flat belt or toothed belt system.

Some hybrid vehicles include an electric motor that can be used to provide drive power to the wheels of the vehicle while the engine and its belt drive system are not running. In this case it may be possible for dirt, snow and/or ice to accumulate in the belt drive system. It has been found that a build-up of dirt, snow and/or ice that may occur in such a situation can cause a ribbed belt of an automotive engine’s belt drive system to jump off a grooved pulley, especially if the engine does not run for a prolonged period during or after a build-up of dirt, snow and/or ice. In particular, it has been found that a grooved belt that drives a BISG pulley may be prone to jumping off the BISG pulley.

It is an aim of the present invention to address disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a belt drive system for an engine, the belt drive system comprising a pulley having a grooved track, a ribbed belt mounted to the pulley and configured to run on the grooved track, and a belt retention device formed separately to the pulley that is mounted to the pulley and extends radially beyond the grooved track in order to prevent the belt from jumping off the pulley in use of the belt drive system. The belt retention device is mounted to the pulley by one or more fasteners which engage with the pulley at one or more attachment points which are not coincident with an axis of rotation of the pulley. The belt retention device comprises a locating feature configured to assist with location of the belt retention device with respect to the pulley, the locating feature being configured to engage an outer radial surface of the pulley.

The belt retention device forms a retaining flange and acts to prevent the ribbed belt from jumping off the pulley and therefore results in a more reliable belt drive system, especially in the case of a belt drive system that may be exposed to contamination by dirt, snow or ice while not running.

It is noted that the jumping failure mode in which a ribbed belt jumps out of the grooves of a pulley and off the end of the pulley due to a build-up of contamination on the belt and/or the pulley that the present invention is intended to prevent is a different failure mode the slipping failure mode sometimes experienced in flat belt systems and toothed belt systems in which a flat belt or toothed belt may slip axially along a pulley.

The belt retention device preferably extends radially beyond the grooved track by a sufficiently great distance to provide a significant barrier to the belt jumping off the pulley. For example, the belt retention device may extend radially beyond the outermost portion of the grooved track by at least 3mm or at least 5mm or at least 10mm.

Since the belt retention device is formed separately to the pulley it is possible to install the belt on the pulley before mounting the belt retention device to the pulley. It may also be possible to remove the belt retention device from the pulley before removing the belt from the pulley during maintenance operations. In this way assembly and maintenance of the belt drive system may be facilitated. In addition, the dimensions of the belt retention device are not constrained by the need to stretch or otherwise fit the belt over the belt retention device, and the belt drive system is not required to be able to generate enough slack to fit the belt over the belt retention device.

It will be appreciated that where the belt retention device is detachably mounted to the pulley the belt retention device may be readily detached from the pulley without damaging either the belt retention device or the pulley.

The fasteners may be formed separately to the belt retention device, for example one or more bolts. The belt retention device may include one or more holes extending therethrough for receiving the one or more fasteners. Alternatively the belt retention device may be attached to the pulley by one or more clip formations. For example, the belt retention device may comprise one or more clip formations, optionally integrally formed with the belt retention device, that are configured to be retained by one or more corresponding formation(s) provided on the pulley.

The belt retention device may extend radially beyond the grooved track of the pulley continuously around the circumference of the pulley.

The belt retention device may comprise a substantially flat plate portion that extends radially beyond the grooved track.

The belt retention device may consist of a substantially flat plate.

The belt retention device may have an at least substantially circular outer shape. The belt retention device may take the form of a circular or annular disk.

The belt retention device may include a central aperture. The central aperture may reduce the mass and material usage of the belt retention device, allow access to the pulley and/or allow drainage from the pulley.

The belt retention device may be located adjacent to an end face of the pulley, for example an end face of the pulley facing away from the engine.

The locating feature may protrude from a pulley-facing surface of the belt retention device,. The locating feature may extend continuously around the circumference of the pulley. The locating feature may be integrally formed with a main body of the belt retention device, and may take the form of a lip that protrudes from the pulley-facing surface of the belt retention device.

The belt drive system may further comprise an engine accessory that is configured to be driven by and/or to drive the belt.

The pulley with the belt retention device mounted thereto may be coupled to an input and/or output of the engine accessory.

The engine accessory may be configured to be driven by the belt in at least one mode of operation, that is to extract power from the belt.

The engine accessory may be configured to drive the belt in at least one mode of operation, that is to transfer drive power to the belt. It will be appreciated that in some cases the engine accessory may be configured to be driven by the belt in at least one mode of operation and also to drive the belt in at least one mode of operation, for example in the case of a belt integrated starter generator.

The engine accessory may be an alternator or a generator.

The engine accessory may be a belt integrated starter generator (BISG). It will be appreciated that a BISG is an alternator or generator that is configured to be driven by the belt in a driven mode of operation and to drive the belt in a powered mode of operation in order to drive the engine, for example when starting the engine. BISGs are also commonly known as belted alternator starters and belt integrated motor generators, among other names. Alternatively the engine accessory may be, for example, a starter motor, a compressor such as an air conditioning compressor, or a pump such as a water pump or a fuel pump.

The belt drive system may include only one engine accessory that is configured to be driven by and/or to drive the belt. Where the belt drive system includes only one engine accessory that is configured to be driven by and/or to drive the belt, the belt drive system may optionally include further belt drives including further belts that are configured to drive other engine accessories.

Alternatively the belt drive system may include a plurality of engine accessories that are configured to be driven by and/or to drive the belt, for example an alternator, a compressor and a pump, in which case each of the engine accessories may be provided with a pulley having a respective separately formed belt retention device mounted thereto.

The belt drive system may further comprise a belt tensioner device or idler pulley configured to engage the belt. The belt tensioner device or idler pulley may be a first belt tensioner device or idler pulley configured to engage the belt on a first side of the pulley, the belt drive system further comprising a second belt tensioner device or idler pulley configured to engage the belt on an opposing second side of the pulley. However, it will be appreciated that the present invention may also be used in a belt drive system that does not include any tensioner devices.

The belt drive system may further comprise a second pulley configured to drive and/or to be driven by the belt. The second pulley may also be provided with a separately formed belt retention device configured to prevent the belt from jumping off the second pulley in use of the belt drive system.

The second pulley may be coupled to a crankshaft of the engine. The second pulley may be coupled directly to the crankshaft, and may be a damper pulley or harmonic balancer that is configured to limit torsional vibration. Alternatively the second pulley may be coupled to the crankshaft indirectly, for example via a further belt drive.

The belt may be configured to be pulled tight in order to be fitted to the pulley, optionally without being stretched and without being rolled onto the pulley. Alternatively the belt may be configured to be stretched in order to be fitted to the pulley and/or to be rolled onto the pulley.

According to a further aspect of the present invention there is provided a belt integrated starter generator system for an engine, the belt integrated starter generator system comprising a belt integrated starter generator and a pulley having a grooved track that is configured to receive a ribbed belt, the pulley being configured to drive or be driven by the belt integrated starter generator, wherein the pulley is provided with a belt retention device formed separately to the pulley that is mounted to the pulley and extends radially beyond the track of the pulley in order to prevent a belt from slipping or jumping off the pulley in use of the belt integrated starter generator system. The pulley may optionally have a grooved track. The belt integrated starter generator system may further comprise a belt, optionally a ribbed belt, configured to run on the pulley.

According to a further aspect of the present invention there is provided an engine comprising a belt drive system as described above or a belt integrated starter generator system as described above. The engine may be an automotive engine, for example a car engine.

According to a further aspect of the present invention there is provided a vehicle comprising an engine as described above. The vehicle may be an automotive vehicle, for example a car.

The vehicle may be a hybrid vehicle further comprising an electric motor that is configured to drive the vehicle. The vehicle may be configured to be driven by the electric motor in an electric mode in which the engine is not running. The present invention is particularly applicable to hybrid vehicles which may be driven in an electric mode in which the engine is not running, which can accumulate dirt, snow or ice in their engine compartments and belt drive systems while being operated in the electric mode, potentially leading to a build-up of dirt, snow or ice around ancillary systems in the engine compartment.

According to a further aspect of the present invention there is provided a kit of parts for forming a belt drive system for an engine, the kit of parts comprising a pulley having a grooved track that is configured to receive a ribbed belt, and a belt retention device formed separately to the pulley that is configured to be mounted to the pulley and to extend radially beyond the grooved track in order to prevent a belt from jumping off the pulley in use of the belt drive system. The belt retention device is mounted to the pulley by one or more fasteners which engage with the pulley at one or more attachment points which are not coincident with an axis of rotation of the pulley. The belt retention device comprises a locating feature configured to assist with location of the belt retention device with respect to the pulley, the locating feature being configured to engage an outer radial surface of the pulley. The kit of parts may further comprise one or more fasteners, for example bolts, for attaching the belt retention device to the pulley. The kit of parts may further comprise a ribbed belt that is configured to be mounted to the pulley and to run on the grooved track. The kit of parts may be used to assemble a belt drive system according to the first aspect of the present invention, and may include any of the features described above in relation to the first aspect of the present invention.

According to a further aspect of the present invention there is provided a method of assembling a belt drive system for an engine, the method comprising mounting a ribbed belt to a pulley having a grooved track, and then mounting a belt retention device to the pulley, the belt retention device extending radially beyond the grooved track in order to prevent the belt from jumping off the pulley in use of the belt drive system. The belt retention device is mounted to the pulley by one or more fasteners which engage with the pulley at one or more attachment points which are not coincident with an axis of rotation of the pulley. The belt retention device comprises a locating feature configured to assist with location of the belt retention device with respect to the pulley, the locating feature being configured to engage an outer radial surface of the pulley. The method may be used in assembling a belt drive system according to the first aspect of the present invention.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination provided they fall within the scope of the appended claims. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination provided they fall within the scope of the appended claims, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figures 1 to 4 illustrate a belt drive system;

Figure 5 illustrates a cross-section view through a pulley of the belt drive system of Figures 1 to 4;

Figure 6 illustrates a vehicle including the belt drive system of Figures 1 to 4; and

Figure 7 illustrates a belt drive system according to an embodiment of the present invention.

DETAILED DESCRIPTION

Figure 6 illustrates a vehicle 100 comprising an engine 101 including a belt drive system 1. As illustrated in Figures 1 to 4, the belt drive system 1 includes a damper pulley 2 that is fitted to the crankshaft of the engine 101 and configured to drive first and second belt drives 10, 20 that together form the belt drive system 1.

The first belt drive 10 comprises a belt integrated starter generator (BISG) 11 that is mounted to the engine 101. The BISG 11 has an input/output shaft to which a BISG pulley 12 is mounted. The BISG pulley 12 is provided with a grooved track 13 on its radially outer surface, as illustrated in Figure 4 and in the cross-section view of Figure 5 taken along the axis of the BISG pulley 12. The first belt drive 10 further comprises a first belt 14 having a plurality of longitudinal ribs provided on an inwardly facing surface thereof. The first belt 14 is mounted to the grooved track 13 of the BISG pulley 12 and to a first grooved track provided on the damper pulley 2, and is configured to run on the damper pulley 2 and the BISG pulley 12 in use of the engine 101. The first belt 14 is configured to drive the BISG 11 in a driven mode of operation in which the BISG 11 is charged by the engine 100 while the engine 100 is running, and in which the BISG may supply electrical power to the main battery of the vehicle 100 or to another battery or capacitor provided in the vehicle 100 (including a battery associated with or forming part of the BISG 11). The first belt 12 is also configured to be driven by the BISG 11 in a powered mode of operation in which the BISG 11 acts to provide drive power to the crankshaft via the damper pulley 2, for example to assist with engine starting operations. The BISG 11 is the only engine accessory that is coupled to the first belt 14 and that forms part of the first belt drive 10, which results in a short belt length that may make fitting the first belt 14 to the pulleys 2, 12 difficult for example due to a reduced stretchable length of belt and a small amount of slack when the belt is not tensioned.

The first belt drive 10 further comprises first and second tensioner devices 15,16 located on opposite sides of the BISG pulley 12. Each of the tensioner devices 15, 16 includes a respective tensioner pulley 15a, 16a that engages an outer (flat) surface of the first belt 14 in order to maintain the first belt in tension during operation of the engine 101 and the belt drive system 1. Each of the tensioner devices 15, 16 is movable between a retracted position as illustrated in Figure 3 for releasing the first belt 14 and generating slack in the first belt 14 in order to facilitate fitting and removal of the first belt, and a deployed position as illustrated in Figures 1 and 2 for engaging and tensioning the first belt 14. It is important to include tensioner devices 15,16 on both sides of the accessory pulley 12 because the accessory pulley 12 is capable of being driven by the first belt 14 in a first mode of operation and of driving the first belt 14 in a second mode of operation (as described above) such that each side of the first belt drive 10 is capable of being both a tight side and a slack side in at least one mode of operation. However, the need to include two tensioner devices 15, 16 at opposite locations in the first belt drive 10 limits the extent to which each of the tensioner devices 15, 16 is able to tension the first belt 14 and generate slack in the first belt 14 when moved into its retracted position.

The BISG pulley 12 is provided with a separately formed, substantially planar, plate-like, annular retaining disk 17 that is attached to the outwardly facing end face of the BISG pulley 12 (that is the face furthest from the engine 101), as illustrated in Figures 1 to 5. The retaining disk 17 includes a plurality of through holes which receive a corresponding plurality of bolts 18 to thereby secure the retaining disk 17 to the BISG pulley 12. The retaining disk 17 extends radially beyond the grooved track 13 of the BISG pulley 12 continuously around the circumference of the BISG pulley 12, and is configured to act as a belt retention device or retaining flange in order to prevent the first belt 14 from jumping off the BISG pulley 12 in use of the engine 101 and the belt drive system 1, thereby improving the reliability of the belt drive system 1. The retaining disk 17 includes a central aperture, which reduces mass and material usage, allows access to the pulley, and allows drainage from the pulley.

The first belt 14 is configured to be installed by first being wrapped around the damper pulley 2 and then being pulled 14 tight and fitted to the BISG pulley 12 while the first and second tensioner devices 15,16 are in their retracted positions. In some cases the step of fitting the first belt 14 to the BISG pulley 12 may include stretching the first belt 14 and/or rolling the first belt 14 onto the BISG pulley 12, although in other cases the first belt drive 10 may include sufficient slack when the first and second tensioner devices are in their retracted positions to enable the first belt 14 to be fitted to the BISG pulley 12 without stretching or rolling the belt. Since the retaining disk 17 is formed separately to the BISG pulley 12, it is possible to mount the retaining disk 17 to the BISG pulley 12 after the first belt 14 has been fitted to the BISG pulley 12. It is therefore not necessary to stretch or otherwise fit the first belt 14 over the retaining disk 17 when installing the first belt 14 on the BISG pulley 12. For this reason the diameter of the retaining disk 17 is not constrained by any need to enable the first belt 14 to be fitted over the retaining disk 17, so it is possible to use a larger diameter for the retaining disk 17 than would be possible with an integrated flange formed at the outer end of the BISG pulley 12 to perform an equivalent retaining function. In addition, the use of a separate retaining disk 17 facilitates assembly of the belt drive system 1 because it is not necessary to stretch or otherwise fit the first belt 14 over any retaining flange when fitting the first belt 14 to the BISG pulley 12.

The use of a separate retaining disk 17 instead of an integrated flange formed at the outer end of the BISG pulley 12 is particularly advantageous in the case of a belt drive 10 including opposing tensioner devices 15, 16 on either side of the pulley 12 because the opposed tensioner devices 15, 16 may not be able to generate enough slack in the belt 14 to allow the belt 14 to be fitted over an integrated or pre-installed retaining flange. In the belt drive 10 illustrated in Figures 1 to 4 it would not be possible to provide the BISG pulley 12 with an integrally formed retaining flange having a diameter significantly larger than that of the grooved track 13 because it would not then be possible to fit the first belt 14 over the retaining flange and onto the BISG pulley 12 bearing in mind the limitation in the amount of stretch available from the short belt and the reduced possibilities for generating slack in the belt caused by the opposed arrangement of the first and second tensioner devices 15, 16.

The retaining disk 17 is readily removable from the BISG pulley 12 by removing the bolts 18. It is therefore also possible to remove the retaining disk 17 from the BISG pulley 12 when it is desired to remove the first belt 14 during maintenance of the belt drive system 1.

The second belt drive 20 comprises a water pump 21 that is mounted to the engine 101 and has an input shaft to which a water pump pulley 22 is mounted. The water pump pulley 22 is driven by a second belt 24 that is mounted to the water pump pulley 22 and to a second grooved track provided on the damper pulley 2 outboard of the first grooved track (on which the first belt 14 of the first belt drive 10 is mounted). As with the first belt 14, the second belt 24 is also a ribbed belt, and may be configured to be pulled tight in order to be fitted to the engine accessory pulley 22, or alternatively to be stretched and/or rolled onto the engine accessory pulley 22. The second belt drive 20 will not be described in detail, although it will be appreciated that the water pump pulley 22 may also be provided with a separately formed retaining disk equivalent to the belt retaining disk 17 of the BISG pulley 12 as described above.

The damper pulley 2 may be provided with one or more retaining flanges located inboard and/or outboard of one or both of the first and second belts 14, 24 for preventing the first and second belts from jumping off the damper pulley. The or each damper pulley flange may be integrally formed with the damper pulley, or alternatively attached to the damper pulley as a separate component.

The vehicle 100 is a hybrid electric vehicle that further comprises an electric motor 102 separate to the engine 101 for proving drive power to the wheels of the vehicle 100. The vehicle 100 is configured to be operated in a purely electric mode of operation in which all drive power is provided by the electric motor 102, and the engine 101 and its belt drive system 1 do not run. In some cases the vehicle may be driven for a prolonged period of time and over a significant distance in the electric mode of operation without running the engine 101 or the belt drive system 1. In this case it is possible for contamination in the form of dirt, snow and/or ice to build up in the belt drive system, for example on the various pulleys 2, 12, 22 and on the first and second belts 14, 24. It has been found that such a build-up may result in the first belt 14 slipping on the BISG pulley 12 or jumping off the BISG pulley 12 when the engine 101 is restarted and the belt drive system 1 begins to operate again, especially when the BISG 11 is operated to help start the engine 101. This problem may become particularly severe where snow is allowed to build up in large quantities in the belt drive system and subsequently turns to ice before the engine 101 is restarted. However, by including the retaining disk 17 on the end face of the BISG pulley 12 the first belt 14 may be prevented from jumping off the BISG pulley 12, thereby leading to a more reliable engine 101 and belt drive system 1.

Figure 7 illustrates a cross-section view taken through a pulley 12 and a retaining disk 17 forming part of a belt drive system 1 according to an embodiment of the present invention. The embodiment illustrated in Figure 7 is generally similar to the example illustrated in Figures 1 to 5 and described above, and so the same reference numbers have been used for equivalent elements, and only differences compared to the example of Figures 1 to 5 will be described. As with the example of Figures 1 to 5, the retaining disk 17 illustrated in Figure 7 takes the form of a circular disk that is attached to an end face of a BISG pulley 12 by a plurality of bolts 18 that are received in a corresponding plurality of through holes provided in the retaining disk 17. However, the retaining disk 17 illustrated in Figure 7 additionally includes an annular locating lip 17a that protrudes from the pulley-facing surface of the retaining disk 17 and engages the radially outer surface of the BISG pulley 12 continuously around the circumference of the BISG pulley 12. The locating lip 17a is configured to assist with location of the retaining disk 17 with respect to the BISG pulley 12, and in particular serves to facilitate correct placement of the retaining disk 17 with respect to the BISG pulley 12 during installation of the retaining disk. The locating lip 17a may also result in a more secure connection between the retaining disk 17 and the BISG pulley 12 after installation of the retaining disk 17, thereby further improving reliability. In addition, the retaining disk 17 illustrated in Figure 7 does not include any central aperture, but instead has a main body portion that covers the entire end face of the BISG pulley 12.

Many modifications may be made to the above-described embodiments without departing from the scope of the present invention as defined in the accompanying claims. For example, in another embodiment the second belt drive 20 could be omitted and the belt drive system 1 could instead only include the first belt drive 10. In addition, the BISG 11 could be replaced by another type of starter motor that is not a BISG. In addition, the first belt drive 10 could alternatively be modified to include a plurality of different engine accessories connected to the first belt 14, for example a water pump and/or an air conditioning compressor in addition to the BISG 11, in which case each of the engine accessories may be provided with a pulley having a respective separately formed belt retention device mounted thereto. Other modifications and variations falling within the scope of the accompanying claims will also be apparent to the skilled person.

Claims

1. A belt drive system for an engine, the belt drive system comprising a pulley having a grooved track, a ribbed belt mounted to the pulley and configured to run on the grooved track, and a belt retention device formed separately to the pulley that is mounted to the pulley and extends radially beyond the grooved track in order to prevent the belt from jumping off the pulley in use of the belt drive system; wherein the belt retention device is mounted to the pulley by one or more fasteners which engage with the pulley at one or more attachment points which are not coincident with an axis of rotation of the pulley; and wherein the belt retention device comprises a locating feature configured to assist with location of the belt retention device with respect to the pulley, the locating feature being configured to engage an outer radial surface of the pulley.

2. A belt drive system according to claim 1, wherein the belt retention device is detachably mounted to the pulley.

3. A belt drive system according to claim 1 or claim 2, wherein the one or more fasteners are formed separately to the belt retention device.

4. A belt drive system according to any preceding claim, wherein the belt retention device extends radially beyond the grooved track of the pulley continuously around the circumference of the pulley.

5. A belt drive system according to any preceding claim, wherein the belt retention device comprises a substantially flat plate portion that extends radially beyond the grooved track.

6. A belt drive system according to any preceding claim, wherein the belt retention device consists of a substantially flat plate.

7. A belt drive system according to any preceding claim, wherein the belt retention device has an at least substantially circular outer shape.

8. A belt drive system according to any preceding claim, wherein the belt retention device is located adjacent to an end face of the pulley.

9. A belt drive system according to any preceding claim, wherein the locating feature protrudes from a surface of the belt retention device.

10. A belt drive system according to any preceding claim, wherein the locating feature extends continuously around the circumference of the pulley.

11. A belt drive system according to any preceding claim, wherein the locating feature is in the form of a lip formed integrally with the belt retention device.

12. A belt drive system according to any preceding claim, further comprising an engine accessory that is configured to be driven by and/or to drive the belt.

13. A belt drive system according to claim 12, wherein the pulley with the belt retention device mounted thereto is coupled to an input and/or output of the engine accessory.

14. A belt drive system according to claim 12 or claim 13, wherein the engine accessory is an alternator or a generator.

15. A belt drive system according to any of claims 12 to 14, wherein the engine accessory is a belt integrated starter generator.

16. A belt drive system according to any preceding claim, further comprising a belt tensioner device configured to engage the belt.

17. A belt drive system according to claim 16, wherein the belt tensioner device is a first belt tensioner device configured to engage the belt on a first side of the pulley, the belt drive system further comprising a second belt tensioner device configured to engage the belt on an opposing second side of the pulley.

18. A belt drive system according to any preceding claim, further comprising a second pulley configured to drive and/or to be driven by the belt.

19. A belt drive system according to claim 18, wherein the second pulley is coupled to a crankshaft of the engine.

20. A belt integrated starter generator system for an engine, the belt integrated starter generator system comprising a belt integrated starter generator and a pulley having a grooved track that is configured to receive a ribbed belt, the pulley being configured to drive or be driven by the belt integrated starter generator, wherein the pulley is provided with a belt retention device formed separately to the pulley that is mounted to the pulley and extends radially beyond the track of the pulley in order to prevent a belt from slipping or jumping off the pulley in use of the belt integrated starter generator system; wherein the belt retention device is mounted to the pulley by one or more fasteners which engage with the pulley at one or more attachment points which are not coincident with an axis of rotation of the pulley; and wherein the belt retention device comprises a locating feature configured to assist with location of the belt retention device with respect to the pulley, the locating feature being configured to engage an outer radial surface of the pulley.

21. An engine comprising a belt drive system according to any of claims 1 to 19 or a belt integrated starter generator system according to claim 20.

22. A vehicle comprising an engine according to claim 21.

23. A vehicle according to claim 22, wherein the vehicle is a hybrid vehicle further comprising an electric motor that is configured to drive the vehicle.

24. A vehicle according to claim 23 configured to be driven by the electric motor in an electric mode in which the engine is not running.

25. A kit of parts for forming a belt drive system for an engine, the kit of parts comprising a pulley having a grooved track that is configured to receive a ribbed belt, and a belt retention device formed separately to the pulley that is configured to be mounted to the pulley and to extend radially beyond the grooved track in order to prevent a belt from jumping off the pulley in use of the belt drive system, wherein the belt retention device is mountable to the pulley by one or more fasteners which engage with the pulley at one or more attachment points which are not coincident with an axis of rotation of the pulley, and wherein the belt retention device comprises a locating feature configured to assist with location of the belt retention device with respect to the pulley, the locating feature being configured to engage an outer radial surface of the pulley.

26. A method of assembling a belt drive system for an engine, the method comprising mounting a ribbed belt to a pulley having a grooved track, and then mounting a belt retention device to the pulley, the belt retention device extending radially beyond the grooved track in order to prevent the belt from jumping off the pulley in use of the belt drive system, wherein the belt retention device is mounted to the pulley by one or more fasteners which engage with the pulley at one or more attachment points which are not coincident with an axis of rotation of the pulley, and wherein the belt retention device comprises a locating feature configured to assist with location of the belt retention device with respect to the pulley, the locating feature being configured to engage an outer radial surface of the pulley.