GB2583474A

GB2583474A - Drive system tensioner testing methods and apparatus

Info

Publication number: GB2583474A
Application number: GB1905942.7A
Authority: GB
Inventors: A Kaminski Allan; John Maile Kevin; Michael Raines Chris; Salter Guy; Qureshi Usman; Hawkins Christopher; Leon Miguel
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2019-04-29
Filing date: 2019-04-29
Publication date: 2020-11-04
Anticipated expiration: 2039-04-29
Also published as: GB2583474B; GB201905942D0

Abstract

A method of testing a belt tensioner 1is provided. The method comprises: arranging the tensioner 1 to tension a belt 16 of a belt drive system 10; driving the belt drive system 10 such that a length of the belt drive system 10 varies at a first frequency as the system is driven; and measuring a load applied by the tensioner 1 to maintain tension in the belt 16 as the length of the belt drive system is varied, in order to determine a performance characteristic of the tensioner 1. A test apparatus 2 for testing the performance of a drive system tensioner 1 is also provided.

Description

Drive system tensioner testing methods and apparatus

Technical Field

The present disclosure relates to drive system tensioner testing methods and apparatus and is particularly, although not exclusively, concerned with drive system tensioner testing methods and apparatus that improve the determination of high frequency performance characteristics of the drive system tensioner

Background

The performance of a tensioner for a belt drive system of an engine, e.g. for motor vehicle, is important for efficient operation of the engine. A tensioner may be tested on the engine production line prior to being installed into the belt drive system of the engine, to ensure that the tensioner has appropriate performance.

Typically, tensioners are tested by using a hydraulic actuator to pulse the tensioner through its range of travel and to measure the stiffness and damping of the tensioner. The operating frequency of the tensioner, at which the tensioner is pulsed when operating within the belt system of the engine, may be greater than the range of frequencies at which the hydraulic actuator can be accurately controlled to pulse the tensioner during testing. As a result, the performance of the tensioner measured during testing at the operating frequency may be less accurate than the performance of the tensioner measured at lower frequencies.

It is desirable to improve the accuracy with which the performance of the tensioner can be measured at the operating frequencies during testing of the tensioner.

Statements of Invention

According to an aspect of the present disclosure, there is provided a method of testing a belt tensioner, the method comprising: arranging the tensioner to tension a belt of a belt drive; driving the belt drive system such that a length of the belt system, e.g. a minimum length or path of the belt to extend around the pulleys of the belt drive system, varies at a first frequency as the system is driven; and measuring a load applied by the tensioner to maintain tension in the belt as the length of the belt drive system is varied, in order to determine a performance characteristic of the tensioner. The performance characteristic may relate to the first frequency.

Driving the belt drive system such that the length of the belt drive system varies as the system is driven may comprise rotating a pulley of the belt drive system about an eccentric axis of the pulley, such that the engaged length of the belt around the pulley varies as the pulley is rotated.

The belt drive system may be driven such that the tensioner is displaced through substantially its complete travel due to the variation in length of the belt drive system.

The tensioner may be an eccentric tensioner, configured such that a portion of the tensioner rotates about an axis of the tensioner as the force applied to the belt by the tensioner varies. The travel of the tensioner may correspond to the range of angles that the portion of the tensioner may be rotated about the axis.

Arranging the tensioner may comprise mounting the tensioner such that load applied by the tensioner against the belt is reacted via a load cell. The method may further comprise determining a force-displacement profile of the drive tensioner. The profile may be a function or plurality of data points relating the force applied by the tensioner to the displacement of the tensioner, e.g. the rotatable portion of the tensioner, from a predetermined position, e.g. relative to a remaining portion of the tensioner. The performance characteristic may comprise the force-displacement profile.

The belt drive system may be driven such that the length of the belt drive system is varied at a frequency greater than 50hz. The method may comprise driving the belt drive system such that the length of the belt drive system is varied at a second frequency. The method may further comprise measuring the load applied by the driver tensioner to maintain tension in the belt system whilst the length is varied at the second frequency, in order to determine the performance characteristic of the drive tensioner relating to the second frequency. The second frequency may be different from, e.g. less or greater than, the first frequency.

According to another aspect of the present disclosure there is provided a test apparatus for testing the performance of a drive system tensioner, the apparatus comprising: a belt drive system comprising: a first pulley; a second pulley; and a belt extending around the first and second pulleys a mount for mounting the drive system tensioner such that tension of the belt is maintained by the drive system tensioner; a motor for driving the belt drive system, wherein the belt drive system is configured such that the length of the belt drive system varies as the belt drive is driven; and a load cell for measuring a load applied by the tensioner to maintain tension in the belt.

The first pulley may be arranged to rotate about an eccentric axis, such that the engaged length of the belt around the first pulley varies as the first pulley rotates. The belt drive system may further comprise a third pulley configured to rotate about a concentric axis of the third pulley. The belt may extend around the first, second and third pulleys.

The load cell may be arranged such that a load applied to the belt by the drive system tensioner is reacted via the load cell. The mount may comprise a mount member rotatably mounted relative to the belt drive system and a moment arm configured to transfer torque from the mount member to the load cell, e.g. as a tensile or compressive load on the load cell.

The mount member may be configured to couple to the drive system tensioner at an axis of the drive system tensioner about which a rotatable portion of the drive system tensioner rotates as the load applied to the belt by the drive system tensioner varies.

The mount member may define a mount axis about which the mount member rotates relative to the drive system. The mount member may be supported on the testing apparatus such that the mount member can rotate about the mount axis relative to the drive system. For example, the mount member may comprise a hollow prism defining an elongate axis of the mount member, which may be the mount axis. The mount member may be configured to couple to the drive tensioner, e.g. to a fixed portion of the drive system tensioner relative to which the rotatable portion rotates, such that the mount axis, e.g. the elongate axis, is aligned with the axis of the drive system tensioner, when the drive system tensioner is coupled to the mount member. The drive system tensioner may thereby be mounted on the test apparatus such that the load applied to the belt is reacted by a torque transmitted though the mount member to the load cell. The mount member may be made from a high strength-to-weight ratio material, such as titanium, an aluminium alloy or a carbon fibre reinforced polymer material.

The second pulley may be configured to rotate about a concentric axis of the second pulley, e.g. concentric with an outer surface of the pulley against which the belt contacts the pulley.

To avoid unnecessary duplication of effort and repetition of text in the specification, certain features are described in relation to only one or several aspects or embodiments of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or embodiment of the invention may also be used with any other aspect or embodiment of the invention.

Brief Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a schematic perspective view of an apparatus for testing a drive tensioner; Figure 2a is a front view of a mount for mounting a drive tensioner on the apparatus shown in Figure 1; Figure 2b is a side view of the mount shown in Figure 2a; and Figure 3 is a flow chart depicted in a method of testing a drive tensioner.

Detailed Description

With reference to Figure 1, an apparatus 2 for testing a drive tensioner comprises a drive system 10, a mount 200 for mounting a drive tensioner 1 on the testing apparatus 2, a load cell 20, and a drive motor 30 for driving the drive system 10.

In the arrangement shown in Figure 1, the drive system 10 is a belt drive system including a first pulley 12, a second pulley 14 and a belt 16, such as a flat belt, a V-belt or a toothed belt, extending around the first and second pulleys 12, 14.

The drive motor 30 is arranged to drive the rotation of the first pulley 12, and the second pulley 14 is driven from the first pulley 12 via the belt 16. The drive motor 30 may comprise a rotary encoder configured to measure the speed of rotation and/or the angular position of a drive shaft 30a of the drive motor 30 as the drive motor 30 is operated.

As depicted, the drive system 10 may further comprise a third pulley 18 and the belt 16 may extend around the first, second and third pulleys 12, 14, 18. The third pulley 18 may be driven by the belt in the same way as the second pulley 14. In other arrangements, the drive system may comprise any other number of pulleys around which the belt 16 extends.

The first pulley 12 may be operatively coupled to the drive motor 30, such that the first pulley is rotated about an axis Ai of the first pulley 12. In the arrangement shown in Figure 1, the first pulley 12 is substantially circular, and the axis Ai is spaced apart from a centre of the circular shape of the first pulley 12. In other words, the axis Ai is an eccentric axis of the first pulley 12. In other arrangements, the first pulley 12 may not be circular. For example, the first pulley may be elliptic or ovate in shape. In such arrangements, the eccentric axis Al may be aligned with the centre of the shape of the first pulley or spaced apart from the centre.

Rotating the first pulley 12 about the eccentric axis Al, causes the length of the belt engaged with the first pulley 12 to vary and thereby causes the length of the belt system 10 to vary. The length of the belt system may be defined as minimum length of belt required for the belt to extend around each of the pulleys in the drive system 10, e.g. so that the belt forms a continuous loop around each of the pulleys in the drive system 10.

The second and third pulleys 14, 18 may be substantially circular and may be configured to rotate about respective axes A2, A3, of the second and third pulleys 14, 18. The axes A2, A3 of the second and third pulleys may be aligned with the centres of the circular shapes of the second and third pulleys 14, 18 respectively. In other words, the axes A2, A3 may be concentric axes of the second the third pulleys 14, 18. The second and third pulleys 14, 18 may be mounted on the testing apparatus 2, e.g. on a frame or base 4 of the testing apparatus, such that the second and third pulleys 14, 18 are free to rotate about their respective axes A2, A3.

The drive tensioner 1 can be mounted on the testing apparatus 2, such that the drive tensioner 1 is arranged to maintain tension in the belt 16 during operation on the drive system 10, e.g. as the length of the drive system 10 varies. In other words, the belt 16 may be held taught between the pulleys 12, 14, 18 by virtue of the operation of the drive tensioner 1.

As depicted, the drive tensioner 1 can be mounted such that the drive tensioner 1 is in contact with the belt 16 between the first pulley 12 and the second pulley 14. The drive tensioner 1 may be mountable such that the belt 16 is deflected, due to the presence of the belt tensioner 1, from a notional straight line extending between the first and second pulleys 12, 14, e.g. from a point 14a, defined by a limit of the engagement of the belt 16 with the second pulley 14, to a point 12a, defined by a limit of the engagement of the belt 16 with the first pulley 12.

In the arrangement shown, the drive tensioner 1 is an eccentric drive tensioner comprising a tensioner pulley la configured to operatively engage the belt, such that the tensioner pulley is rotatably driven by the belt 16, about a concentric axis Ac of the tensioner pulley 1, as the drive system 10 operates.

The tensioner pulley la is pivotally coupled to a tensioner body 1b of the drive tensioner 1 via a pivot axis Ap. The pivot axis Ap is spaced apart from the concentric axis Ac of the tensioner pulley la, such that the position of the concentric axis Ac can be varied relative to the tensioner body lb by pivoting the tensioner pulley 1 a about the pivot axis A. In particular, the position of the concentric axis Ac of the tensioner pulley la can be varied such that the deflection of the belt 16 by the tensioner 1 is varied, in order to maintain tension in the belt 16. The position of the tensioner pulley 1 a is able to vary relative to the tensioner body 1b through a range of angles defining a travel of the tensioner 1. The tensioner 1 may comprise a tensioner position sensor configured to determine, e.g. measure, the position of the tensioner pulley la relative to the tensioner body 1 b.

The drive tensioner 1 further comprises a biasing element configured to bias the tensioner pulley la into a position at which deflection of the belt 16 by the tensioner is at a maximum. The tensioner 1 thereby acts to maintain tension in the belt 16 during operation of the drive system 10, e.g. as the length of the drive system 10 changes.

The testing apparatus 2 may be configured such that the length of the drive system 10 is varied by an amount that causes the tensioner pulley 1a to move through substantially its full range of travel to maintain tension in the belt 16. For example, the shape of the first pulley 12 and/or the position of the axis Al about which the first pulley 12 is rotated may be configured such that the length of the drive system 10 varies by a suitable amount.

The tensioner 1 is mountable on the testing apparatus 2 by the mount 200, such that the force applied to the belt 16 by the tensioner 1 is reacted through the load cell 20. As depicted, the mount 200 may comprise a mount member 210 for coupling to the tensioner 1. The mount member 210 may be rotatably mounted on the testing apparatus 2, e.g. on the frame or base 4, by one or more radial bearings 40, such as ball or roller bearings, so that the mount member 210 can rotate, e.g. substantially freely rotate, relative to the testing apparatus 2 about a mount axis AM.

The mount member 210 may be configured to couple to the tensioner body lb such that the mount axis AM is aligned with the pivot axis Ap of the tensioner 1. The load applied by the tensioner 1 to the belt 16 may therefore be reacted by a toque about the mount axis AM transmitted through the mount member 210.

The mount 200 further comprises a moment arm 220 for coupling the mount member 210 to the load cell 20. In particular, a first end 20a of the load cell is coupled to the moment arm 220 and a second end 20b of the load cell is fixed relative to the testing apparatus 2, e.g. to the frame or base 4. The moment arm 220 and load cell 20 may be arranged such that the torque load carried by the mount member 210 is transmitted to the load cell 20 via the moment arm 220 as a compressive/tensile, e.g. pure compressive or tensile, load applied to the load cell 20. The load applied to the load cell 20 can thereby be used to determine the force being applied to the belt 16 by the tensioner 1.

With reference to Figures 2a and 2b, the mount member 210 may be substantially prism shaped. For example, the mount member 210 may be substantially cylindrical. The prism shape of the mount member 210 may define a longitudinal axis of the mount member 210 which may be aligned with the mount axis AM. The mount member 210 may be configured such that an inertia of the mount member 210 about the mount axis AM is minimised. In particular, the mount member 210 may be hollow and/or a maximum radius of the mount member 210 about the mount axis AM may be minimised. The mount member 210 may be made from a material having a high strength to weight ratio, such as titanium, an aluminium-magnesium alloy material or a composite material, such as a carbon fibre reinforced polymer, so that a wall thickness of the hollow mount member can be reduced without reducing the load bearing capabilities of the mount member 210. In this way, the accuracy with which the load applied by the tensioner to the belt 16 can be measured may be increased.

The moment arm 220 of the mount 200 may similarly be formed from a material having a high strength to weight ratio, such that the mass of the moment arm 220 can be minimised. Additionally, the moment arm 220 may be shaped such that a second moment of area of the moment arm 220, in a plane parallel to the mount axis AM, is increased, e.g. compared to a square prism. For example, a width of the moment arm 220 in a direction perpendicular to the mount axis AM may be greater than a thickness of the moment arm in a direction parallel with the mount axis AM. Furthermore, the width of the moment arm 220 in a direction perpendicular to the mount axis AM may be greater at a proximal end 220a of the moment arm, at the connection with the mount member 210, that at a distal end 220b of the moment arm 220, e.g. at the connection with the load cell.

As shown Figures 2a, the mount member 210 may comprise a threaded portion 210a comprising a thread, e.g. an internal thread. The mount member 210 may be configured to couple to the tensioner 1 via the thread. A wall thickness of the mount member 210 may be increased at the threaded portion to enable the thread to be formed. Alternatively, the threaded portion may comprise an insert coupled to the mount member 210. For example, when the mount member 210 is formed from a carbon fibre reinforced polymer, the threaded portion 210a may comprise an insert formed from a metal material, such as titanium or an aluminium alloy, coupled, e.g. adhered, to the mount member 210. The insert may be arranged inside the hollow prism of the mount member 210.

In other arrangements of the disclosure, the testing apparatus 2 may be configured in any other way to enable any other form of drive tensioner to be mounted on the testing apparatus 2 to maintain tension in the belt 16, and such that the load applied to the belt by the tensioner can be transmitted to the load cell 20.

Returning to Figure 1, the load cell 20 may be coupled to a computing device 100, e.g. a controller, configured to record the load being applied to the load cell 20, e.g. in a memory associated with the computing device. The computing device 100 may be configured to determine the force being applied to the belt 16 by the tensioner 1 based on the load being applied to the load cell 20. The computing device 100 may determine a performance characteristic of the tensioner 1, e.g. based on the load applied to the load cell 20.

The computing device 100 may be coupled to the drive motor 30 and may be configured to receive information from the rotary encoder of the drive motor 30, such as the speed of rotation of the drive motor and/or the angular position of the drive motor shaft 30a. In some arrangements, the computing device 100 may be configured to control the operation of the drive motor 30.

The computing device 100 may be configured to determine a position of the tensioner pulley 1a relative to the tensioner body 1b. For example, the computing device 100 may determine the length of the drive system 10 based on the eccentricity of the first pulley 12 and the particular angular position of the drive motor shaft 30a and may determine the position of the tensioner pulley la based on the drive system length. Additionally or alternatively, the computing device 100 may be operatively coupled to the tensioner 1, e.g. the tensioner position sensor, and may receive information from the tensioner position sensor indicating the position of the tensioner pulley la relative to the tensioner body 1 b.

The performance characteristic of the tensioner may be a force-displacement characteristic of the tensioner, e.g. a function or trend line relating the position of the tensioner pulley la relative to the tensioner body 1b with the force applied by the tensioner 1 against the belt 16, or a set of data points including values of the position of the tensioner pulley la relative to the tensioner body 1b and the corresponding force being applied by the tensioner 1.

As described above, the tensioner 1 may comprise a biasing element configured to bias the position of the tensioner pulley la. The performance characteristic of the tensioner may comprise a stiffness characteristic of the biasing element, which may be dependent of the position of the tensioner pulley la.

The tensioner 1 may further comprise a damping element configured to damp the movement of the tensioner pulley la relative to the tensioner body 1b. Additionally or alternatively, the movement of the tensioner pulley may be damped due to the way in which the tensioner 1 is constructed, e.g. separately from the inclusion of a dedicated damping element. The performance characteristic of the tensioner may comprise a damping characteristic of the tensioner 1.

With reference to Figure 3, the testing apparatus 2 may be operated according to a method 300. The method 300 comprises a first step 302 in which the tensioner 1 is arranged on the testing apparatus 2, such that the belt 16 is tensioned by the tensioner.

The method 300 further comprises a second step 304, in which the belt system in driven such that the length of the belt system varies, e.g. at a first frequency, as the system is driven. As described above, the second step 304 may be performed by driving the rotation of the first pulley 12 of the drive system 10 about an eccentric axis Ai of the first pulley 12.

The method 300 further comprises a third step 306, in which the load applied to the belt by the tensioner 1, in order to maintain tension in the belt, is measured. As described above, the load may be measured by the load cell 20 arranged in the load path between the tensioner mount 200 and a base 4 of the testing apparatus 2. A performance characteristic of the tensioner may be determine based on the measured load, e.g. by the computing device 100 coupled to the load cell 20. As described above, the performance characteristic may comprise a force-displacement profile of the tensioner, e.g. relating the force applied by the tensioner against the belt 16 to the position of the tensioner pulley la relative to the tensioner body lb. Additionally or alternatively, the performance characteristic may comprise a stiffness and/or damping characteristic of the tensioner 1.

After the tensioner has been tested, the tensioner may be installed into a drive system, e.g. a belt drive system, of an engine system, e.g. on a motor vehicle. It may be desirable for the tensioner 1 to be tested, e.g. using the testing apparatus 2, under conditions similar to those expected to be experienced when operating the engine system. The drive system 10 may therefore be operated such that the frequency at which the length of the drive system 10 is varied, e.g. between a maximum length and a minimum length, is substantially equal to a frequency at which the tension in the drive system of the engine system may vary during its operation. For example, the testing apparatus may be operated such that the length of the drive system 10 varies at a frequency of greater than or equal to 50Hz.

In some arrangements, it may be desirable for the tensioner 1 to be tested at more than one frequency. The method 300 may comprise driving the belt system 10 such that the length of the belt system varies at a second frequency. The second frequency may be different from, e.g. greater or less than, the first frequency. The second frequency may also be greater than or equal to 50Hz. Alternatively, the second frequency may be less than 50Hz.

When the drive system is operated at the second frequency, the loads applied to the load cell 20 may be measured and a further performance characteristic of the tensioner may be determine, e.g. relating to the second frequency. Alternatively, the performance characteristic determined when the drive system was operated at the first frequency may be extending to include data relating to operation at the second frequency.

The following additional, numbered statements of invention are also included within the specification and form part of the present disclosure: Statement 1. A method of testing a belt tensioner, the method comprising: arranging the tensioner to tension a belt of a belt drive system; driving the belt drive system such that a length of the belt drive system varies at a first frequency as the system is driven; and measuring a load applied by the tensioner to maintain tension in the belt as the length of the belt drive system is varied, in order to determine a performance characteristic of the tensioner.

Statement 2. The method of statement 1, wherein driving the belt system, such that the length of the belt drive system varies as the system is driven, comprises rotating a pulley of the belt drive system about an eccentric axis of the pulley, such that the engaged length of the belt drive system around the pulley varies as the pulley is rotated.

Statement 3. The method of statement 1 or 2, wherein the belt drive system is driven such that the tensioner is displaced through substantially its complete travel due to the variation in length of the belt drive system.

Statement 4. The method of any of the preceding statements, wherein arranging the tensioner comprises mounting the tensioner such that load applied by the tensioner against the belt is reacted via a load cell.

Statement 5. The method of any of the preceding statements, wherein the method further comprises: determining a force-displacement profile of the drive tensioner, wherein the performance characteristic comprises the force-displacement profile.

Statement 6. The method of any of the preceding statements, wherein the belt drive system is driven such that the length of the belt drive system is varied at a frequency greater than 50hz.

Statement 7. The method of any of the preceding statements, wherein the method further comprises: driving the belt drive system such that the length of the belt drive system is varied at a second frequency; and measuring the load applied by the driver tensioner to maintain tension in the belt whilst the length is varied at the second frequency, in order to determine the performance characteristic of the drive tensioner relating to the second frequency.

Statement 8. A test apparatus for testing the performance of a drive system tensioner, the apparatus comprising: a belt drive system comprising: a first pulley; a second pulley; and a belt extending around the first and second pulleys; a mount for mounting the drive system tensioner such that tension of the belt is maintained by the drive system tensioner; a motor for driving the belt drive system, wherein the belt drive system is configured such that the length of the belt drive system varies as the belt drive is driven; and a load cell for measuring a load applied by the tensioner to maintain tension in the belt.

Statement 9. The apparatus of statement 8, wherein the first pulley is arranged to rotate about an eccentric axis, such that the engaged length of the belt around the first pulley varies as the first pulley rotates.

Statement 10. The apparatus of statement 8 or 9, wherein the load cell is arranged such that a load applied to the belt by the drive system tensioner is reacted via the load cell.

Statement 11. The apparatus of any of statements 8 to 10, wherein the mount comprises a mount member rotatably mounted relative to the belt drive system and a moment arm configured to transfer torque from the mount member to the load cell.

Statement 12. The apparatus of statement 11, wherein the mount member is configured to couple to the drive system tensioner at an axis of the drive system tensioner about which a rotatable portion of the drive system tensioner rotates as the load applied to the belt by the drive system tensioner varies.

Statement 13. The apparatus of statement 11 or 12, wherein the mount member comprises a hollow prism defining an elongate axis of the mount member.

Statement 14. The apparatus of statements 12 and 13, wherein the mount member is configured to couple to the drive tensioner such that the elongate axis is aligned with the axis of the drive system tensioner, when the drive system tensioner is coupled to the mount member.

Statement 15. The apparatus of any of statements 11 to 14, wherein the mount member is made from a high strength-to-weight ratio material, such as titanium, an aluminium alloy or a carbon fibre reinforced polymer material.

Statement 16. The apparatus of any of statements 8 to 15, wherein the second pulley is configured to rotate about a concentric axis of the second pulley.

Statement 17. The apparatus of any of statements 8 to 16, wherein the belt drive system comprises a third pulley configured to rotate about a concentric axis of the third pulley, and wherein the belt extends around the first, second and third pulleys.

It will be appreciated by those skilled in the art that although the invention has been described by way of example, with reference to one or more exemplary examples, it is not limited to the disclosed examples and that alternative examples could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

Claims 1. A method of testing a belt tensioner, the method comprising: arranging the tensioner to tension a belt of a belt drive system; driving the belt drive system such that a length of the belt drive system varies at a first frequency as the system is driven; and measuring a load applied by the tensioner to maintain tension in the belt as the length of the belt drive system is varied, in order to determine a performance characteristic of the tensioner.
2. The method of claim 1, wherein driving the belt system, such that the length of the belt drive system varies as the system is driven, comprises rotating a pulley of the belt drive system about an eccentric axis of the pulley, such that the engaged length of the belt drive system around the pulley varies as the pulley is rotated.
3. The method of claim 1 or 2, wherein the belt drive system is driven such that the tensioner is displaced through substantially its complete travel due to the variation in length of the belt drive system.
4. The method of any of the preceding claims, wherein arranging the tensioner comprises mounting the tensioner such that load applied by the tensioner against the belt is reacted via a load cell.
5. The method of any of the preceding claims, wherein the method further comprises: determining a force-displacement profile of the drive tensioner, wherein the performance characteristic comprises the force-displacement profile.
6. The method of any of the preceding claims, wherein the belt drive system is driven such that the length of the belt drive system is varied at a frequency greater than 50hz.
7. The method of any of the preceding claims, wherein the method further comprises: driving the belt drive system such that the length of the belt drive system is varied at a second frequency; and measuring the load applied by the driver tensioner to maintain tension in the belt whilst the length is varied at the second frequency, in order to determine the performance characteristic of the drive tensioner relating to the second frequency.
8. A test apparatus for testing the performance of a drive system tensioner, the apparatus comprising: a belt drive system comprising: a first pulley; a second pulley; and a belt extending around the first and second pulleys; a mount for mounting the drive system tensioner such that tension of the belt is maintained by the drive system tensioner; a motor for driving the belt drive system, wherein the belt drive system is configured such that the length of the belt drive system varies as the belt drive is driven; and a load cell for measuring a load applied by the tensioner to maintain tension in the belt.
9. The apparatus of claim 8, wherein the first pulley is arranged to rotate about an eccentric axis, such that the engaged length of the belt around the first pulley varies as the first pulley rotates.
10. The apparatus of claim 8 or 9, wherein the load cell is arranged such that a load applied to the belt by the drive system tensioner is reacted via the load cell.
11. The apparatus of any of claims 8 to 10, wherein the mount comprises a mount member rotatably mounted relative to the belt drive system and a moment arm configured to transfer torque from the mount member to the load cell.
12. The apparatus of claim 11, wherein the mount member is configured to couple to the drive system tensioner at an axis of the drive system tensioner about which a rotatable portion of the drive system tensioner rotates as the load applied to the belt by the drive system tensioner varies.
13. The apparatus of claim 11 or 12, wherein the mount member comprises a hollow prism defining an elongate axis of the mount member.
14. The apparatus of claims 12 and 13, wherein the mount member is configured to couple to the drive tensioner such that the elongate axis is aligned with the axis of the drive system tensioner, when the drive system tensioner is coupled to the mount member.
15. The apparatus of any of claims 11 to 14, wherein the mount member is made from a high strength-to-weight ratio material, such as titanium, an aluminium alloy or a carbon fibre reinforced polymer material.
16. The apparatus of any of claims 8 to 15, wherein the second pulley is configured to rotate about a concentric axis of the second pulley.
17. The apparatus of any of claims 8 to 16, wherein the belt drive system comprises a third pulley configured to rotate about a concentric axis of the third pulley, and wherein the belt extends around the first, second and third pulleys.