Tensioning a belt on a starter generator

Abstract

Device (101) for tensioning a belt (102) on a starter generator (103), the device (101) comprising: a first pulley (105) and a second pulley (106); a holding structure (104) for holding the first pulley (105) and the second pulley (106), the holding structure (104) comprising a fixed part (112) that is attached adjacent to the starter generator (103); wherein the first pulley (105) serves to provide tension in the belt (102) of the starter generator (103) on a first side of the starter generator (103), the first pulley (105) is held by the holding structure (104) and is attached such that it rotates about its own axis of rotation (109) relative to the holding structure (104); wherein the second pulley (106) is held by the holding structure (104) and serves to provide tension in the belt (102) on a second side of the starter generator (103);wherein the holding structure (104) comprises: a first part (115) which holds the first pulley (105) and is fixed in such a way that it rotates relative to the stationary part (112), a second part (116) which holds the second pulley (106) and is fixed in such a way that it rotates relative to the stationary part (112), and a separating device which connects the first and second parts (115, 116) of the holding structure (104), wherein the separating device is configured to limit the positioning of the second pulley (106) depending on the position of the first pulley (105);wherein the holding structure (104) is configured to allow the rotational movement of the axis of rotation (109) of the first pulley (105) about the axis (108) of the starter generator (103), and wherein the device (101) comprises a stop device (110) which is arranged to limit the movement of the axis of rotation (109) of the first pulley (105) about the axis (108) of the starter generator (103); wherein the stop device (110) comprises: at least one first stop element (119) fixed to the first part (115) of the holding structure (104), at least one second stop element (120) fixed to the stationary part (112) of the holding structure (104), and at least one third stop element (119B) fixed to either the first part (115) or the second part (116) of the holding structure (104);wherein the at least one first stop element (119) and the at least one third stop element (119B) serve to limit the movement of the first pulley (105) by abutting the at least one second stop element (120) before the resultant forces acting on the first and second pulleys (106) are balanced by the separating device which connects the first and second parts (115, 116) of the holding structure (104).

Description

TECHNICAL FIELDThe present disclosure relates to tensioning a belt on a starter generator. More particularly, but not exclusively, it relates to the tensioning of a belt on a starter generator of a hybrid vehicle.Aspects of the present invention relate to an apparatus and method for tensioning a belt on a starter generator and to a propulsion system and vehicle including such an apparatus.PRIOR ARTHybrid vehicles are known that include a belt-driven integrated starter generator (BISG). The BISG is also referred to as a BSG (Belt-Driven Starter Generator), BSA (Belt-Driven Starter Alternator), and a MGU (Motor Generator Unit). For purposes of the present document, the BISG is referred to as a "starter generator.".DE 10 2013 217 514 A1 discloses, for example, a belt tensioner for an auxiliary unit belt drive of an internal combustion engine. The belt tensioner includes a housing portion, a tensioning portion rotatably supported on the housing portion, a single tensioning roller supported on the tensioning portion and biasing the belt, and a spring that applies torque to the tensioning portion to generate the belt biasing. The spring is a flat spiral spring which is hooked on the tensioning part with an outer spring leg bent radially outwards and on the housing part with an inner spring leg bent radially inwards, which has an arcuate spring contact on which the inner spring winding of the spiral spring is radially supported with an end section extending as far as the inner spring leg and the arcuate shape of which is composed of at least two different radii of curvature (R 1, R 2) which become smaller along the winding end section as far as the inner spring leg.DE 199 26 615 A1 discloses a tensioning device for traction means such as belt rollers or chains, having a housing-like part in which a tensioning means and a spring element for tensioning the traction means, said tensioning device being mountable on a unit of the traction means drive having a drive shaft, with the housing-like part being arranged in a rotationally fixed manner so as to surround the drive shaft, wherein the tensioning means comprises two tensioning arms which are mounted in the housing-like part such that they can rotate about a common axis and with respect to one another and which are spring-loaded by means of the common spring element which is held at one end on one tensioning arm and at the other end on the other tensioning arm.US 4 758 208 discloses a belt tensioning device for a combined vehicle starter generator, wherein the belt tensioning device uses the shift reaction torque occurring upon a change from the generation mode to the cranking mode or back to automatically select one of two tensioning arms to tension the slack side of a belt.Finally, DE 10 2012 209 0288 A1 discloses a tensioning device for a starter generator belt drive of an internal combustion engine and a starter generator having such a tensioning device.Generally, the starter generator includes a pulley connected to the crankshaft of the internal combustion engine by a belt. Depending on whether the starter generator is driven (in an alternator mode) or whether it provides a driving force, the belt is tensioned on one side of the starter generator pulley or on the other side. To control the tension on the slack side of the belt, tension pulleys are provided to increase the tension on the slack side.Such an arrangement is shown in FIG. 8. In this example, the belt 801 extends from the crankshaft pulley 802 of the internal combustion engine and around the starter generator pulley 803. The crankshaft pulley 802 and the starter generator pulley 803 are arranged to rotate clockwise in the view shown in the figure.The belt also passes around a first tension pulley 804 on a right side of the starter generator pulley 803 and passes around a second tension pulley 805 on the left side of the starter generator pulley 803. In this arrangement, each of the tension pulleys 804 and 805 is supported by a respective arm 806 and 807 which is mounted to allow the arm to freely rotate about the starter generator pulley 803. However, the positions of the tension pulleys 804 and 805 are limited by the action of the belt 801 on the pulleys and the action of a spring mechanism 808 connecting the two arms 806 and 807. Such a tension arrangement, in which the position of one pulley results from the position of the other pulley, can be referred to as a decoupling tension device.Tension pulleys 804 and 805 are shown in a nominal position in FIG. 8 that they may assume when the vehicle is off. However, when the starter generator is in its drive mode and is used to generate torque, the tension on the left side 809 of the belt 801 is increased, and the arms 806 and 807 holding the pulleys 804 and 805 are rotated clockwise about the starter generator pulley 803 as the left side of the belt aligns under tension.Similarly, when the engine is operating and the starter generator is in its alternator mode, the tension on the right side 810 of the belt 801 is increased and the arms 806 and 807 holding the pulleys 804 and 805 are rotated counter-clockwise about the starter generator pulley 803 as the right side of the belt aligns under tension. Such hybrid vehicles may also include a conventional starter motor connected to the engine used to crank the engine. In this case, the crankshaft pulley generates an abrupt increase in tension on the right side 810 of the belt 801, straightening the right side 810 of the belt 801. This situation is illustrated in Fig. 9, which also shows a problem with this arrangement.The problem is that more space than desired must be provided around the starter generator to accommodate the pulleys 804 and 805 in their extreme positions. If sufficient space is not provided, one or both of the pulleys could inadvertently come into contact with another part of the vehicle. In the example of FIG. 9, sufficient space has not been provided for the pulley 804, and thus has come into contact with a vehicle-mounted component 901 as shown by the arrow A. In this example, the vehicle-mounted component 901 is an air duct.It is an object of the present invention to overcome this problem.SUMMARY OF THE INVENTIONAspects of the embodiments of the present invention provide an apparatus and method for tensioning a belt on a starter generator and a propulsion system and vehicle according to the following claims.According to one aspect of the present invention there is provided an apparatus for tensioning a belt on a starter generator, the apparatus comprising: a support structure for supporting a first pulley and a second pulley, the support structure being mounted adjacent to a starter generator; and a first pulley for providing tension in a belt of the starter generator, the first pulley being supported by the support structure and being mounted to rotate about its own axis of rotation relative to the support structure; the support structure being configured to enable rotational movement of the axis of rotation of the first pulley about the axis of the starter generator, and the apparatus comprising stop means arranged to limit movement of the axis of rotation of the first pulley about the axis of the starter generator.This provides the advantage that a smaller space can be provided to accommodate the first pulley.In an embodiment of the present invention, the support structure is attached to the starter generator and the first pulley is adapted to provide tension in a belt on a first side of the starter generator and the apparatus comprises a second pulley supported by the support structure to provide tension in the belt on a second side of the starter generator.In an embodiment, the support structure comprises: a first part supporting the first pulley, a second part supporting the second pulley, and a separator connecting the first and second parts of the support structure, wherein the separator is configured to limit the positioning of the first pulley depending on the position of the second pulley. In such an embodiment, the separating means comprises a spring means connecting the first and second parts of the supporting structure, and the spring means may comprise a spring extending around the outside of a pulley of the starter generator.In one embodiment, the stop device comprises at least one first stop element which is fixed to the holding structure and at least one second stop element in relation to the starter generator. In such embodiments, the stop may include a plurality of first stops spaced about the axis of the integrated starter generator and a plurality of second stops spaced accordingly. In such embodiments, the stop device may comprise at least three first stop elements and a corresponding number of second stop elements. In some such embodiments, the at least one second stop element is attached to the starter generator. In some such embodiments, the at least one second stop element is fixed to the support structure. In some such embodiments, the at least one first stop member and / or the at least one second stop member comprises an elastically deformable member, and the elastically deformable member may be formed of rubber or a synthetic polymer.This provides the advantage that the elastically deformable component can reduce noise and force peaks that can occur during operation of the device.In one embodiment, the stop is configured to limit movement of the axis of rotation of the first pulley about the axis of the starter generator in both clockwise and counter-clockwise directions.This provides the advantage of reducing the space required to accommodate the first and second pulleys.According to another aspect of the present invention, there is provided a drive system for a vehicle according to claim 14.According to another aspect of the present invention there is provided a vehicle as claimed in claim 15.According to yet another aspect of the present invention there is provided a method of providing tension in a belt on a starter generator, the method comprising the steps of: supporting a first pulley and a second pulley adjacent a starter generator to enable the first pulley to rotate about its own axis of rotation and to enable rotational movement of the axis of rotation about the axis of the starter generator and to limit movement of the axis of rotation of the first pulley about the axis of the starter generator.In an embodiment of the method, the first pulley and the second pulley are supported by a support structure, and the method includes attaching the support structure to the starter generator.In one embodiment, the method includes applying a belt around the first pulley, the second pulley, and a pulley of the starter generator such that the first pulley is disposed on a first side of the starter generator on the belt and the second pulley is disposed on a second side of the starter generator on the belt.In one embodiment of the method, the process of holding a first pulley and a second pulley comprises holding the first pulley on a first part and holding the second pulley on a second part, and a separator is configured to limit the positioning of the second pulley depending on the position of the first pulley. The separating means may comprise spring means connecting the first and second parts. The spring means may comprise a spring which extends around the outside of a pulley of the starter generator.In an embodiment of the method, the first pulley and the second pulley are supported by a support structure that also supports at least one first stop member, and limiting the movement of the rotation axis comprises fixing at least one second stop member relative to the starter generator. A plurality of first stops may be spaced about the axis of the starter generator, and the method may include fixing a plurality of correspondingly spaced second stops. The method may include fixing the at least one second stop member to the starter generator.According to another aspect of the present invention there is provided an apparatus for tensioning a belt on a starter generator, the apparatus comprising: a support structure for supporting a first pulley and a second pulley, the support structure being configured to be mounted adjacent a starter generator; and a first pulley for providing tension in a belt of the starter generator, the first pulley being supported by the support structure and being mounted to rotate about its own axis of rotation relative to the support structure; the support structure being configured to enable rotational movement of the axis of rotation of the first pulley about the axis of the starter generator, and the apparatus comprising stop members arranged to limit movement of the axis of rotation of the first pulley about the axis of the starter generator.According to another aspect of the present invention there is provided an apparatus for tensioning a belt on a starter generator, the apparatus comprising: a support structure for supporting a first pulley; and a first pulley for providing tension in a belt, the first pulley supported by the support structure and being mounted to rotate about its own axis of rotation with respect to the support structure; the support structure being configured to enable rotational movement of the axis of rotation of the first pulley about a second axis, and the apparatus comprising stop members arranged to limit movement of the axis of rotation of the first pulley about the second axis.The scope of this application is expressly intended to include the various aspects, embodiments, examples and alternatives set forth in the paragraphs above, in the claims and / or in the following description and drawings, and in particular the individual features thereof may be adopted independently or in any combination. This means that all embodiments and / or features of any embodiment may be combined in any manner and / or combination, provided that these features are not incompatible. Applicant reserves the right to alter any originally filed claim or to submit any new claim accordingly, including the right to alter any originally filed claim to depend on and / or integrate any feature of any other claim, although in this manner it has not been previously claimed.BRIEF DESCRIPTION OF THE DRAWINGSOne or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 shows a front view of an exemplary apparatus 101 for tensioning a belt 102 mounted on a starter generator 103; FIGS. 2A and 2B show a rear perspective view and a front perspective view, respectively, of the device 101 separated from the starter generator 103; FIG. 3 schematically shows the apparatus 101 adjacent to a starter generator 103 located within a vehicle 301; FIG. 4 shows a front view of the device 101 adjacent to the starter generator 103 located adjacent to the internal combustion engine 303; FIG. 5 shows the device 101 when the first stop members 119 abut against the second stop members 120 after rotation from the configuration shown in FIG. 4 ; FIG. 6 shows an alternative device 101B; FIG. 7 shows a method 700 for providing tension in a belt on a starter generator; FIG. 8 shows a known arrangement for providing tension in a belt on a starter generator; and FIG. 9 shows the arrangement of FIG. 8 operating when the starter generator is in its alternator mode.DETAILED DESCRIPTIONThe figures illustrate an apparatus 101 for tensioning a belt 102 on a starter generator 103, the apparatus 101 comprising: a support structure 104 for supporting a first pulley 105 and a second pulley 106, the support structure 104 being mounted adjacent to a starter generator 103; and a first pulley 105 for providing tension in a belt 102 of the starter generator 103, the first pulley 105 being supported by the support structure 104 and being mounted so as to rotate about its own axis of rotation 109 with respect to the support structure 104; the support structure 104 being configured to enable the rotational movement of the axis of rotation 109 of the first pulley 105 about the axis 108 of the starter generator 103, and the apparatus 101 comprising a stop device 110 arranged to limit the movement of the axis of rotation 109 of the first pulley 105 about the axis 108 of the starter generator 103.FIG. 1 shows a front view of an example apparatus 101 for tensioning a belt 102 mounted on a starter generator 103. The device 101 comprises a support structure 104 providing the support structure 104 for supporting a first pulley 105 and a second pulley 106. The support structure 104 is secured adjacent the starter generator 103 and extends around the pulley 107 of the starter generator 103. The pulley 107 of the starter generator 103 is operatively connected to the rotor (not shown) of the starter generator so that, in operation, it rotates about its own axis 108. (Axis 108 extends into the sheet in Figure 1.)The apparatus 101 also includes a first pulley 105 for providing tension in the belt 102 of the starter generator 103. The first pulley 105 is supported by the support structure 104 and is fixed so as to be able to rotate about its own axis of rotation 109 relative to the support structure 104. (The axis of rotation 109 of the pulley 105 also extends into the blade in Figure 1 and is therefore parallel to the axis 108 of the starter generator 103.) The support structure 104 is configured to enable rotational movement of the rotational axis 109 of the first pulley 105 about the axis 108 of the starter generator 103. The device 101 further comprises a stop device 110 arranged to limit the movement of the rotation axis 109 of the first pulley 105 about the axis 108 of the starter generator 103.As described in detail below, limiting the movement of the rotation axis of the first pulley 105 in such a manner results in less space being required for accommodating the device 101.In the example of FIG. 1, the apparatus 101 also includes a second pulley 106 supported by the support structure 104 for providing tension in the belt 102 of the starter generator 103. In the arrangement of FIG. 1, the first pulley 105 is arranged to provide tension in the belt 102 on a first side 102A of the starter generator 103, and the second pulley 106 is arranged to provide tension in the belt 102 on a second side 102B of the starter generator 103.The second pulley 106 is also fixed so as to be able to rotate about its own axis of rotation 111 relative to the support structure 104, and the support structure is configured to allow the axis of rotation 111 of the pulley 106 to rotate about the axis 108 of the starter generator 103.The support structure 104 of the device 101 is fastened to the starter generator 103 in FIG. 1. However, it should be appreciated that the support structure 104 may be attached to another part of the vehicle to which the starter generator is attached, provided it is attached adjacent the starter generator pulley 107. For example, in an alternative arrangement, the support structure 104 may be supported by the engine block.The support structure 104 comprises a fixed part 112 comprising a plurality (in this case three) of lugs 113 defining holes (201 in Figure 2A) for receiving screws 114 to enable screwing of the support structure 104 to the starter generator 103.The support structure 104 includes a first part 115 on which the first pulley 105 is mounted so as to be able to rotate about its own axis of rotation 109 with respect to the first part 115. The first part 115 is itself fixed to rotate relative to the fixed part 112 so that when the fixed part 112 is rigidly fixed to a starter generator, the axis of rotation 109 of the pulley 105 can rotate about the axis 108 of the starter generator.The support structure 104 includes a second part 116 on which the second pulley 106 is mounted so as to be able to rotate about its own axis of rotation 111 with respect to the second part 116. The second part 116 is itself fixed to rotate relative to the fixed part 112 so that, when the fixed part 112 is rigidly fixed to a starter generator, the axis of rotation 111 of the pulley 106 can rotate about the axis 108 of the starter generator.A rear perspective view of the device 101 separated from the starter generator 103 is shown in FIG. 2A. This view of the device 101 shows the fixed part 112 having the three noses 113 defining the screw holes 201. A front perspective view of the device 101 separated from the starter generator 103 is shown in FIG. 2B.The fixed part 112 comprises a central portion 202, a rear portion 203 and a front portion 204. The central portion 202 has a cylindrical inner surface, and the rear portion 203 and the front portion 204 extend radially outward from the rear and front ends of the central portion 202, respectively. The first part 115 and the second part 116 are mounted between the front portion 204 and the rear portion 203 on bearings around the central portion 202 such that the first part and the second part can rotate independently of each other around the central portion 202. By this mechanism, the axes 109, 111 of the first and second pulleys 105 and 106 can rotate about the axis of the starter generator ( 103 in FIG. 1 ).The support structure 104 further comprises a separator device connecting the first and second parts 115 and 116 of the support structure 104. The separator is configured to limit the positioning of the first pulley 105 depending on the position of the second pulley 106. In the present example, the isolator includes a spring means connecting the first and second parts 115, 116 of the support structure 104 such that the spring means can be tensioned in use to cause the pulleys 105 and 106 to exert tension forces on the belt 102. In the present example, the spring device comprises a spring 207 which extends around the fixed part 112. The spring 207 has a first end 117 fixed to the first part 115 and a second end 118 fixed to the second part 116. In the absence of a belt, as shown in FIG. 2, the first part 115 and the second part 116 may freely rotate about the fixed part 112, but the angular spacing of the first pulley 105 and the second pulley 106 is approximately maintained by the spring 207. (The angular spacing may vary to some extent due to the flexibility of spring 207.)In the present example, the spring means is a single arcuate spring 207. However, other spring means may be used as known in the art. For example, the first and second members may be provided with arms spaced apart from the first and second pulleys, and a coil spring may be connected between the arms to maintain the relative angular positioning of the first and second pulleys.The stop device 110 comprises at least one first stop element 119 fixed to the support structure 104 and at least one second stop element 120 which may be fixed with respect to the starter generator 103. The first stop elements 119 may be fixed to the first part 115 of the support structure 104, and the second stop elements 120 may be fixed to the fixed part 112 of the support structure 104. In the present example, the second stop elements are fixed to the front portion 204 of the fixed part 112. In an alternative embodiment, second stop members may be provided that are configured to be directly attached to the starter generator.In the present example, the stop 110 includes a plurality of first stop members 119 angularly spaced about the axis 108 of the integrated starter-generator 103 and a plurality of second stop members 120 respectively spaced. Thus, during operation, each of the first stops 119 is arranged to contact a corresponding second stop 120, substantially at the same time as the other first stops 119.In the present example, the stop device 110 comprises three first stop elements and a corresponding number of second stop elements. However, other embodiments are also provided that include more than three first stops and a corresponding number of second stops, while other embodiments are provided that include less than three first stops and a corresponding number of second stops.The first stop members 119 may be disposed at an equal angular distance about the axis 108 of the starter generator 103. In this way, undesired forces are minimized, which may tend to lead to distortion of the holding structure 104.The first stop elements 119 and / or the second stop elements 120 may comprise an elastically deformable component. For example, at least a portion of the first stop members 119 and / or the second stop members 120 may include an elastically deformable member formed of rubber or a synthetic polymer that is elastically deformable, such as rubber. In the present example, the second stop elements 120 are provided with an elastically deformable component 121.During operation, movement (counterclockwise in FIG. 1 ) of the first stop members 119 repeatedly brings the first stop members into contact with the second stop members 120, thereby stopping further movement in this direction. By positioning an elastic deformable member 121 at the contact position, the impact of the first stop members 119 on the second stop members 120 is cushioned, so that noise resulting from the impact is reduced, and force peaks resulting from the impact can also be reduced.The apparatus 101 is shown in FIG. 3 adjacent to a starter generator 103 located within a vehicle 301. The vehicle 301 has a propulsion system 302 that includes an internal combustion engine 303, the starter generator 103, the belt 102, and the device 101 that is arranged to provide tension in the belt 102.During operation of the vehicle, engine 303 is used to provide the torque required to power-move vehicle 301, but as is known from hybrid vehicles, a portion of the power generated by engine 303 may be used to drive starter generator 103 which generates electricity in its generator mode. The generated electricity is stored in one or more batteries 304.A portion of the force generated by the motor 303 may also be used to power other accessories, for example an air conditioner compressor 305.In a propulsion mode, the starter generator 103 may be used to start the movement of the vehicle 301, and may provide power boost to assist the engine 303 as needed.The vehicle 301 may also include a separate starter motor 306 used to start the engine 303 when the vehicle is being started.The apparatus 101 is shown in FIG. 4 adjacent to the starter generator 103 located adjacent to the internal combustion engine 303, the engine 303 comprises a crankshaft on which a crankshaft pulley 401 is mounted, and a water pump with a water pump pulley 402. In the present example, the vehicle also includes an air conditioner compressor 305 with an air conditioner pulley 403.The belt 102 passes around the crankshaft pulley 401, the water pump pulley 402, the air conditioning pulley 403, the first pulley 105 of the device 101, the starter generator pulley 107, the second pulley 106 of the device 101 and a pulley 404 back again to the crankshaft pulley 401.The device 101 is shown in FIG. 4 in an orientation that it can assume when the vehicle is out of service. Tension can be generated in the belt 102 by the action of the pulleys 105 and 106, which tension is pressed against the belt by the action of the spring 207. When the engine 303 and the starter generator 103 are not providing power, the voltage on the first side 102A of the belt 102 and the second side 102B of the belt 102 may be equal, resulting in the configuration of FIG. 4.During operation of the engine 303 or the starter motor 306 (shown in FIG. 3 ), the crankshaft is rotated clockwise as shown in FIG. 4 and the tension on the first side 102A of the belt 102 is increased while the tension on the second side 102B of the belt is decreased. As a result, the tension on the first side of the belt 102A provides a resultant force to the first pulley 105, thereby forcing the first pulley axis 109 about the starter generator axis 108 (counterclockwise in FIG. 4 ), and the first side 102A of the belt 102 tends to become more straight. That is, the first side 102A of the belt 102 wraps around the first pulley at a smaller angle. Therefore, this movement causes the resultant force applied to the first pulley 105 by the belt 102 to be reduced.The first part 115 of the support structure 104 on which the first pulley 105 is mounted is connected by the spring 207 to the second part 116 on which the second pulley 106 is mounted. As a result, this movement (counter-clockwise at the starter generator axis 108) of the first pulley 105 also causes similar movement of the second pulley 106. This movement of the second pulley 106 causes the second side 102B of the belt 102 to be wrapped around the second pulley 106 at a greater angle and increases the resulting force applied to the belt 102 by the second pulley 105.In the absence of the stop 110, the rotation of the pulleys 105 and 106 about the axis 108 of the starter generator 103 would continue until the resulting forces exerted by the first side 102A and the second side 102B of the belt 102 on the pulleys 105 and 106 are balanced. However, in the present case, the stop device 110 is configured to limit the counterclockwise movement of the rotation axis 109 of the first pulley 105 about the axis 108 of the starter generator 103. As such, the first pulley 105 may rotate about the starter generator axis 108 until the first stops 119 abut the second stops 120.The device 101 is shown in FIG. 5 in a state in which the first stop elements 119 abut against the second stop elements 120 after such a rotation. The stop members 119 and 120 have limited the counterclockwise movement of the first pulley 105 to its position shown in FIG. 5. In the present example, a relatively large gap A (greater than 20 mm) thus exists between the first pulley 105 and an air duct 501 that is also present in the engine compartment of the vehicle.An alternative device 101B is shown in Figure 6. The apparatus 101B may be identical to the apparatus 101 of FIG. 1 except that it is provided with third stop members 119B in addition to the first stop members 119 and second stop members 120 described above. The third stop members 119B are fixed to the second part 116 of the support structure 104 that supports the second pulley 106. As illustrated in FIG. 6, a third stopper 119B is disposed between each of the first stopper 119 and the closest second stopper 120 in the clockwise direction.When the starter generator 103 is in its alternator mode, the first stop members 119 and the second stop members 120 of the device 101B act to limit the movement of the axis 109 of the first pulley 105, in the same manner as the device 101.When the starter generator 103 is in a drive mode, for example, when torque is provided to start the motion of the vehicle, the tension on the second side 102B of the belt 102 is increased and reduced on the first side 102A of the belt 102. The increased tension on the second side 102B of the belt generates a greater resultant force on the second pulley 106 compared to the resultant force provided from the first side 102A of the belt 102 on the first pulley 105. Consequently, the second pulley 106 is urged clockwise about the axis 108 of the starter generator 103, and due to the spring 207 connecting the second part 116 to the first part 115 of the support structure 104, the first pulley 105 is also urged clockwise. In the absence of the third stop members 119B, this movement would continue until the resulting forces on the first and second pulleys 105 and 106 are again balanced. However, in the present case, this movement is limited by the third stop elements 119B, which abut against the second stop elements 120.In the present example, the second stop members 120 are provided with an elastic portion 601A, 601B on each of both sides thereof. When the first and second pulleys 105 and 106 are rotated counterclockwise about the axis 108 of the starter generator 103, the first stopper members 119 abut against an elastic portion 601A on one side of the second stopper members 120, and when the first and second pulleys 105 and 106 are rotated clockwise about the axis 108 of the starter generator 103, the second stopper members 119B abut against an elastic portion 601B on the opposite side of the second stopper members 120.In an alternative arrangement to that of FIG. 6, the position of the second pulley 106 in both the clockwise and counter-clockwise directions may be limited by limiting the positioning of the first pulley 105. For example, the third set of stops 119B, like the first set of stops 119, may be fixed to the first part 115 that holds the first pulley 105. Alternatively, the stop elements 119 can be made sufficiently wide to provide the function of the first and third stop elements, respectively.A method 700 for providing tension in a belt on a starter generator is illustrated in FIG. 7. The method includes, at block 701, providing a support structure for a first pulley and a second pulley adjacent to a starter generator. For example, block 701 may include providing the support structure 104 as described above with respect to FIG. 1, thereby allowing the first pulley 105 to rotate about its own axis of rotation 109 and allowing rotational movement of the axis of rotation 109 about the axis 108 of the starter generator 103. This process may include mounting the first and second pulleys on bearings to the first and second portions 115 and 116, respectively, of the support structure 104, and mounting the first and second portions 115 and 116 on bearings to the fixed portion 112 of the support structure. The spring 207 may then be attached at each of its ends to the first and second parts 115 and 116.In block 702 of the method, a stop device is provided for limiting the movement of the rotation axis 109 of the first belt pulley 105 about the axis 108 of the starter generator 103, to which the holding structure can be located adjacent. The fixing of the stop device to the support structure 104 can be effected, for example, by fixing first stop elements 119 to the first part 115 and fixing second stop elements 120 to the fixed part 112, for example, by welding.The method may include attaching the support structure to the starter generator such that the first and second pulleys are disposed adjacent to a pulley of the starter generator. Thereafter, a belt may be applied around the first pulley, the second pulley, and the starter generator such that the first pulley is disposed on a first side of the starter generator on the belt and the second pulley is disposed on a second side of the starter generator on the belt.In an embodiment, the support structure comprises: a first part supporting the first pulley, a second part supporting the second pulley, and a separator connecting the first and second parts of the support structure, wherein the separator is configured to limit the positioning of the first pulley depending on the position of the second pulley. The isolator may comprise spring means connecting the first and second parts of the support structure, and the spring means may comprise a spring, such as spring 207, which extends around the outside of a pulley of the starter generator.In an embodiment, the stop device comprises at least one first stop element (such as the stop elements 119) fixed to the support structure (such as the first part 115 of the support structure 104). Then, the method includes fixing at least one second stop element (such as stops 120) relative to the starter generator. This can be achieved by arranging the second stop elements on a fixed part (such as the fixed part 113) of a support structure which is then fixed to the starter generator by screws (114). Alternatively, the at least one second stop element may be directly fixed to the starter generator.Although in the above paragraphs, embodiments of the present invention have been described with reference to various examples, it should be understood that changes may be made to the present examples without departing from the scope of the present invention as set forth in the following claims.The features described in the above description can also be used in combinations other than the combinations explicitly described here.Although functions have been described with reference to certain features, these functions may also be performable by other features whether or not described herein.Although functions have been described with reference to certain embodiments, these functions may also be present in other embodiments whether or not described herein.Although the foregoing description has sought to draw attention to those features of the present invention which are believed to be of particular importance, it should be understood that the Applicant claims protection with respect to any patentable features or combinations of features referred to above and / or illustrated in the drawings, whether or not referred to that particular meaning.

Claims

An apparatus (101) for tensioning a belt (102) on a starter generator (103), the apparatus (101) comprising: a first pulley (105) and a second pulley (106); a support structure (104) for supporting the first pulley (105) and the second pulley (106), the support structure (104) comprising a fixed part (112) attached adjacent to the starter generator (103); wherein the first pulley (105) is for providing tension in the belt (102) of the starter generator (103) on a first side of the starter generator (103), the first pulley (105) is supported by the support structure (104) and is attached to rotate about its own axis of rotation (109) relative to the support structure (104); wherein the second pulley (106) is supported by the support structure (104) and is for providing tension in the belt (102) on a second side of the starter generator (103); the support structure (104) comprising: a first portion (115) supporting the first pulley (105) and mounted to rotate relative to the fixed portion (112), a second portion (116) supporting the second pulley (106) and mounted to rotate relative to the fixed portion (112), and a disconnect connecting the first and second portions (115, 116) of the support structure (104), the disconnect configured to limit the positioning of the second pulley (106) depending on the position of the first pulley (105); wherein the support structure (104) is configured to allow rotational movement of the rotational axis (109) of the first pulley (105) about the axis (108) of the starter generator (103), and wherein the apparatus (101) comprises a stop (110) arranged to limit the movement of the rotational axis (109) of the first pulley (105) about the axis (108) of the starter generator (103); wherein the stop (110) comprises: at least one first stop element (119) fixed to the first part (115) of the support structure (104), at least one second stop element (120) fixed to the fixed part (112) of the support structure (104), and at least one third stop element (119B) fixed to either the first part (115) or the second part (116) of the support structure (104); wherein the at least one first stop element (119) and the at least one third stop element (119B) serve to limit the movement of the first pulley (105) by abutting against the at least one second stop element (120) before the resulting forces acting on the first and second pulleys (106) are compensated by the separating device connecting the first and second parts (115, 116) of the supporting structure (104).The apparatus (101) of claim 1, wherein the support structure (104) is attached to the starter generator (103).The apparatus (101) of claim 1 or claim 2, wherein the separating means comprises spring means connecting the first and second parts (115, 116) of the holding means (104).The device (101) according to claim 3, wherein the spring means comprises a spring (207) extending around the outside of a pulley (107) of the starter generator (103).The apparatus (101) according to any one of claims 1 to 4, wherein the stop device (110) comprises a plurality of first stop elements (119) spaced apart about the axis (108) of the starter generator (103) and a plurality of second stop elements (120) spaced apart respectively.The apparatus (101) according to any one of claims 1 to 4, wherein the stop device (110) comprises at least three first stop elements and a corresponding number of second stop elements (120).The device (101) according to any of the preceding claims, wherein the at least one second stop element (120) is attached to the starter generator (103).The device (101) according to any one of the preceding claims, wherein the at least one first stop element (119) and / or the at least one second stop element (120) comprises an elastically deformable member (121).The device (101) according to claim 8, wherein the elastically deformable member (121) is formed of rubber or a synthetic polymer.The device (101) according to any of the preceding claims, wherein the stop device (110) is configured to limit the movement of the rotation axis (109) of the first pulley (105) about the axis (108) of the starter generator (103) in both clockwise and counter-clockwise directions.A drive system (302) for a vehicle (301) comprising an internal combustion engine (303), a starter generator (103), a belt (102) and a device (101) according to any preceding claim, the device (101) being arranged to provide tension in the belt (102).A vehicle (301) comprising an internal combustion engine (303), a starter generator (103), a belt (102) and a device (101) according to any one of claims 1 to 10, the device (101) being arranged to provide tension in the belt (102).A method (700) of providing tension in a belt (102) on a starter generator (103), the method (700) comprising the steps of: maintaining a first pulley (105) and a second pulley (106) adjacent to a starter generator (103) to allow the first pulley (105) to rotate about its own axis of rotation (109) and to allow rotational movement of the axis of rotation (109) about the axis (108) of the starter generator (103); limiting movement of the axis of rotation (109) of the first pulley (105) about the axis (108) of the starter generator (103); wherein the first pulley (105) and the second pulley (106) are supported by a support structure (104) comprising a fixed part (112), and the method comprises attaching the fixed part (112) of the support structure (104) to the starter generator (103); comprising applying a belt (102) around the first pulley (105), the second pulley (106), and a pulley (107) of the starter generator (103) such that the first pulley (105) is disposed on a first side of the starter generator (103) on the belt (102) and the second pulley (106) is disposed on a second side of the starter generator (103) on the belt (102); wherein the holding of the first pulley (105) and the second pulley (106) comprises: holding the first pulley (105) on a first part (115) of the holding structure (104) fixed to rotate relative to the fixed part (112) and holding the second pulley (106) on a second part (116) of the holding structure (104) fixed to rotate relative to the fixed part (112), and wherein a separator connecting the first part (115) and the second part (116) is configured to limit the positioning of the second pulley (106) depending on the position of the first pulley (105); wherein the holding structure (104) further comprises at least one first stop element (119), at least one second stop member (120) and at least one third stop member (119B), and limiting movement of the axis of rotation (109) of the first pulley (105) about the axis (108) of the starter generator (103) holds fixing the at least one first stop member (119) to the first part (115) of the support structure (104), fixing the at least one second stop member (120) to the fixed part (112) of the support structure (104), fixing the at least one third stop member (119B) to either the first or second part (116) of the support structure (104), and abutting one of the at least one first stop member (119) and the at least one third stop member (119B) against the at least one second stop member (120), before the resulting forces acting on the first and second pulleys (106) are compensated by the separator connecting the first and second parts (116) of the support structure (104).The method (700) of claim 13, wherein the separating means comprises a spring means connecting the first and second parts (116).The method (700) of claim 14, wherein the spring means comprises a spring (207) extending around the outside of a pulley (107) of the starter generator (103).The method (700) of any of claims 13 to 15, wherein a plurality of the first stop members (119) are spaced apart about the axis (108) of the starter generator (103), and the method (700) comprises fixing a plurality of correspondingly spaced apart ones of the second stop members (120).The method (700) of any of claims 13 to 16, comprising fixing the at least one second stop element (120) to the starter generator (103).

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