Tensioning device, drive system, vehicle and tensioning method

Abstract

The invention relates to a device (10) for tensioning a deformable transmission element, comprising a means (18) for adjusting the tension in the transmission element, and a resilient member (20), the adjustment means (18) being movable through a first stroke, the device being capable of tensioning the transmission element (12) with a first tension by way of the resilient member (20), the deformation whereof is limited, and, beyond the first stroke, through a second stroke, the device being capable of tensioning the transmission element (12) with a second additional tension by way of the adjustment means (18), the second stroke depending on the second tension to be applied in the transmission element (12). The invention further relates to a transmission system, a vehicle and a tensioning method.

Description

[0001] TENSIONING DEVICE, DRIVE SYSTEM, VEHICLE AND TENSIONING METHOD

[0002] Technical field

[0003] The present invention relates to a device for tensioning a transmission element, a drive system with the device, a vehicle with the system and a tensioning method.

[0004] Prior art

[0005] There are devices for tensioning a drive belt. These devices can be spring-loaded tensioners. The disadvantage of these devices is the occurrence of vibrations during operation. One solution to vibration is the addition of damping elements, the disadvantages of which are their cost and complexity. These devices can also be fixed tensioners during use. The disadvantage of these devices is that they do not allow sufficient tension to be applied to the belt in operating modes where the load is potentially high. Alternatively, if very high tension is applied to the belt to cope with these operating modes with high loads, this creates excessive friction and significant stress on all the components of the transmission.

[0006] US3785220 describes a belt clutch device comprising a drive pulley and a pulley driven by the drive pulley using an endless belt initially loosely mounted around the drive and driven pulleys. An arm is pivotally mounted at one end thereof within the perimeter of the belt. A belt tension pulley is rotatably mounted at the other end of the arm and in contact with the inner surface of the belt. A return spring connected to the arm moves the tension pulley away from the inner surface of the belt. An actuating device, and a connecting member connected between the actuating device and the arm, is adapted to pivot the arm against the force of the return spring and into a predetermined angular relationship with the belt, such that the tension pulley fully tensions the belt.This document does not provide for tensioning the belt by the spring. In fact, the spring is, on the contrary, a return spring, to put the arm back in a disengaged position. Document US6030305 describes a belt tensioning device. The device allows a belt to be tensioned between two pulleys - without acting on the belt itself, but by increasing the center distance between the pulleys. The device in this document makes it possible to provide a reference for the tension in order to be able to obtain a correct adjustment with tension springs whose length changes over time, possibly because they have undergone plastic deformation under constant load.

[0007] Generally speaking, current devices do not allow adaptation to a wide range of transmitted torque.

[0008] There is a need for a tensioning device that can accommodate a wide range of transmitted torque.

[0009] Statement of the invention

[0010] To this end, the invention proposes a device for tensioning a deformable transmission element comprising a means for adjusting the tension in the transmission element, and an elastic member, the adjustment means being able to be movable: According to a first stroke, the device being able to tension the transmission element with a first tension by the elastic member whose deformation is limited, and, beyond the first stroke, According to a second stroke, the device being able to tension the transmission element with a second additional tension by the adjustment means, the second stroke being a function of the second tension to be applied in the transmission element.

[0011] According to one variant, the device further comprises a carrier, the device being capable of tensioning the transmission element via the carrier. According to one variant, the device comprises a roller movable in rotation relative to the carrier, the carrier being capable of tensioning the transmission element via the roller.

[0012] According to one variant, the elastic member is on the wearer.

[0013] According to a variant, the deformation of the elastic member is limited at the stop.

[0014] According to a variant, the deformation of the elastic member is limited in abutment by the wearer.

[0015] According to a variant, the deformation of the elastic member is limited in abutment by the adjustment means coming into abutment against the carrier at the end of the first stroke or by the elastic member coming into abutment against the carrier.

[0016] According to a variant, according to the first stroke of the adjustment means, the wearer of the device is able to tension the transmission element with the first tension by the elastic member whose deformation is limited, the adjustment means urging the elastic member into deformation in a limited manner by abutment against the wearer, and, beyond the first stroke, according to the second stroke of the adjustment means, the wearer of the device is able to tension the transmission element with the second additional tension by the adjustment means urging the wearer, the second stroke being a function of the second tension to be applied in the transmission element.

[0017] According to one variant, the elastic member is chosen from the group comprising a leaf spring, a helical spring, a spiral torsion spring, a stud made of elastic material, a structural part designed to provide the appropriate stiffness for the tension to be placed in the transmission element.

[0018] According to one variant, the adjustment means is a screw or an eccentric.

[0019] The invention also relates to a drive system, comprising a deformable transmission element, the device as described previously, the device being capable of tensioning the transmission element.

[0020] According to a variant, the system further comprises a casing, the transmission element and the device being at least partly in the casing, the adjustment means being accessible from outside the casing, the casing comprising a viewport intended to control the first stroke and / or the second stroke of the adjustment means.

[0021] According to a variant, the device is further capable of tensioning the transmission element during elongation of the transmission element during operation, the elastic member compensating for the elongation of the transmission element.

[0022] The invention also relates to a vehicle with the drive system as described above.

[0023] Alternatively, the vehicle is a bicycle or a motorcycle.

[0024] The invention also relates to a method of tensioning a transmission element in a drive system, the method comprising

[0025] The provision of a system as described above,

[0026] The tensioning of the transmission element by the device, comprising

[0027] - According to the first stroke of the adjustment means, the tensioning of the transmission element with a first tension by the elastic member whose deformation is limited, then, beyond the first stroke,

[0028] - According to the second stroke of the adjustment means, tensioning the transmission element with a second additional tension by the adjustment means, the second stroke being a function of the second tension to be applied in the transmission element.

[0029] According to a variant, the device further comprises a carrier, the device being capable of tensioning the transmission element via the carrier, the deformation of the elastic member is limited in abutment by the adjustment means coming into abutment against the carrier at the end of the first stroke or by the elastic member coming into abutment against the carrier.

[0030] According to a variant, the system further comprises a casing, the transmission element and the device being at least partly in the casing, the adjustment means being accessible from outside the casing, the casing comprising a sight glass, the method comprising monitoring the first stroke and / or the second stroke of the adjustment means through the sight glass. According to a variant, the method further comprises tensioning the transmission element by the elastic member of the device during an elongation of the transmission element during operation, the elastic member compensating for the elongation of the transmission element.

[0031] The use in this document of the verb "to understand", its variants, as well as its conjugations, cannot in any way exclude the presence of elements other than those mentioned. The use in this document of the indefinite article "un", "une", or of the definite article "le", "la" or "I'", to introduce an element does not exclude the presence of a plurality of these elements.

[0032] The terms "first", "second", "third", etc. are used in this document exclusively to differentiate between different elements, without implying any order between these elements.

[0033] All of the preferred embodiments and all of the advantages of the tensioning device according to the invention are transposed mutatis mutandis to the present drive system, vehicle and tensioning method and vice versa. The different embodiments can be considered alone or in combination.

[0034] Brief description of the figures

[0035] Other characteristics and advantages of the present invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended figures which show: figure 1, a schematic view according to an example of the invention; figure 2, a schematic view of the operation of figure 1; figure 3, a schematic view of the operation of figure 1; figure 4, a view of another example of the invention; figure 5, a view of the operation of figure 4; figure 6, a view of the operation of figure 4; figure 7, a graph showing the elongation as a function of the tension; figure 8, a graph showing the tensioning. The drawings of the figures are not to scale. Similar elements are generally denoted by similar references in the figures. Within the context of this document, identical or similar elements may bear the same references.Furthermore, the presence of reference numbers or letters in the drawings cannot be considered as limiting, including when these numbers or letters are indicated in the claims.

[0036] Detailed description of embodiments of the invention

[0037] The invention relates to a device for tensioning a deformable transmission element. The device comprises a means for adjusting the tension in the transmission element and an elastic member. The adjustment means is capable of being movable along a first stroke, the device being capable of tensioning the transmission element with a first tension by the elastic member whose deformation is limited. Beyond the first stroke, the adjustment means is capable of being movable along a second stroke, the device being capable of tensioning the transmission element with a second additional tension by the adjustment means, the second stroke being a function of the second tension to be applied in the transmission element. The device makes it possible to tension the transmission element for a normal load operating mode and to tension the transmission element for a high load operating mode.The device can therefore be adapted to different operating modes.

[0038] The figures show a tensioning device 10 in a drive system 11 and the operation. The device 10 makes it possible to tension a transmission element 12 in the drive system 11. The transmission element 12 may be deformable. The transmission element 12 may be deformable in the sense that its shape can be altered. The transmission element 12 may be deformable in the sense that elongation can occur in the transmission element 12. The transmission element 12 may be, in particular, a chain, a belt or a flexible band. If the transmission element 12 is a belt, the belt is preferably made of a flexible material and is preferably toothed or notched on its inner surface (see Figure 4). The transmission element 12 may transmit power between two or more wheels or pulleys 14, 16.The transmission element 12 makes it possible to transmit power between parallel rotating axes. The transmission element 12 makes it possible to transfer power between the pulley 14 and the pulley 16 - possibly in both directions, depending on the direction of rotation of the pulleys. One of the pulleys, for example the pulley 14, may be driven by a motor not visible in the figures. The power of the pulley 14 may be transferred by the transmission element 12 to the pulley 16. In particular, during the tensioning of the transmission element 12, the center distance between the pulleys 14, 16 (or more) remains invariable.

[0039] The device 10 may also comprise a means 18 for adjusting the tension in the transmission element 12. The device 10 acts (directly) on the transmission element 12 to tension it (while maintaining the center distance of the pulleys and not by separating the pulleys). The device 10 (directly) stresses the transmission element 12. The device 10 is in contact with the transmission element to tension it. By adjusting the adjustment means 18, the tension in the transmission element 12 can be adjusted, determined. The adjustment means 18 is capable of being movable, which makes it possible to adjust the tension in the transmission element 12. The adjustment means 18 may be movable in translation and / or in rotation. The adjustment means 18 may be movable along a stroke, which makes it possible to adjust the tension in the transmission element. The nature of the stroke depends on the type of mobility of the adjustment means 18.The adjustment means 18 can be movable according to a first stroke 13 and a second stroke 15, depending on the desired tension to be placed in the transmission element 12. According to each of the two strokes, the adjustment means 18 is movable (adjustable) continuously (therefore according to a non-discrete number of positions of the adjustment means) to ensure precise adjustment of the tension. The tensioning of the transmission element 12 is obtained at the end of the first and second strokes. The adjustment means 18 can be a screw. The screw is movable in rotation and in translation, the rotation of the screw allowing the translation of the screw. The screw has a linear translational stroke (which depends on the rotation given to the screw). The adjustment means 18 can be an eccentric. The eccentric is movable in rotation. The eccentric has an angular rotational stroke.The adjustment means 18 may also be thickness shims, a slide whose degree of freedom can be locked, an adjustment lever which can be locked, a cam and its locking mechanism, a hydraulic piston, a pneumatic, hydraulic, piezoelectric, electromagnetic actuator as well as the possible transmission and the associated locking mechanism. The adjustment means is any means allowing the adjustment of the force and the associated locking mechanism, by an external member (such as a ratchet or a cleat) or by irreversibility.

[0040] The device 10 may also comprise an elastic member 20. The elastic member 20 makes it possible to exert a force to tension the transmission element 12. The deformation of the elastic member 20 makes it possible to tension the transmission element 12. The adjustment means 18 is capable of urging the elastic member 20 into deformation. By the mobility over its travel, the adjustment means 18 is capable of urging the elastic member 20 into deformation. The deformation of the elastic member 20 takes place during the travel of the adjustment means 18. Preferably, the deformation of the elastic member 20 is limited. The elastic member 20 is capable of deforming up to a limit. The deformation of the elastic member 20 is possible to a certain extent. The elastic member 20 is capable of deforming until it comes to a stop (mechanical stop).The elastic member 20 can be chosen from the group comprising a leaf spring, a helical spring, a spiral torsion spring, a stud made of elastic material, or a structural part designed to provide the appropriate stiffness for the tension to be placed in the transmission element 12. Other examples of elastic members can be given.

[0041] The adjustment means 18 is movable along the first stroke 13. The device 10 is then able to tension the transmission element 12 with a first tension by the elastic member. The stiffness of the elastic member 20 transmits a force 17 into the transmission element 12 which is tensioned. In a state of stress of the elastic member 20 imposed by the adjustment means 18, the elastic member 20 undergoes a given deformation. The deformation of the elastic member 10 tensiones the transmission element 12.

[0042] Beyond the first stroke 13, the adjustment means 18 is movable according to the second stroke 15. In other words, the movement (displacement) of the adjustment means 18 until the end of the first stroke 13 then drives the adjustment means 18 in the second stroke 15. As can be seen in the figures, the second stroke beyond the first stroke means that the second stroke is in the extension of the first stroke. In the second stroke, the adjustment means 18 extends its movement further than in the first stroke. The device 10 is then able to tension the transmission element 12 with a second additional tension by the adjustment means. The second imparted tension, transmitted by the adjustment means 18 in the transmission element 12 is added to the first imparted tension, transmitted by the elastic member 20 in the transmission element 12.The second stroke 15 is a function of the second tension to be applied in the transmission element. Depending on the second tension to be applied, the adjustment means 18 is moved along the second stroke. During the movement of the adjustment means 18 over the second stroke, the elastic member 20 is maintained at its limited deformation, possibly at the stop. This makes it possible to maintain and control the first tension by the elastic member 20 during the application of the second tension, during the second stroke of the adjustment means 18. The sum of the two tensions (total tension) makes it possible to obtain the desired tension, that is to say which allows optimal operation for nominal use of the transmission element 12, as determined during the design of the drive system 11. The first tension and the second tension (and therefore the total pressure) are applied precisely, over the entire two strokes of the adjustment means 18.The adjustment means 18 transmits a force 19 into the transmission element 12 which is set to the desired tension.

[0043] In the example of Figures 1-3, the device 10 puts the transmission element 12 under tension by a movement which can be translational. In the example of Figures 4-6, the device 10 puts the transmission element 12 under tension by a movement which can be rotational.

[0044] The device 10 may further comprise a carrier 24. The device 10 is capable of tensioning the transmission element 12 via the carrier 24. The carrier is movable. The carrier 24 may be movable in translation according to figures 1-3, or in other words according to a linear guide. The device 10 then tensioned the transmission element 12 by the movement of the carrier in translation. The carrier 24 according to figures 1-3 is then a slider 24 movable in translation. The carrier 24 in the form of a slider can push or pull the transmission element 12 to tension it. The carrier 24 may be movable in rotation in figures 4-6, or in other words according to a rotation guide. The device 10 then tensioned the transmission element 12 by the movement of the carrier in rotation. The carrier 24 according to figures 4-6 is then a lever 24 movable in rotation.

[0045] It is also possible that the carrier 24 and the elastic member 20 are combined.

[0046] The carrier 24 can stress the transmission element 12 by being in direct contact against the transmission element 12. Preferably, the device 10 can comprise a roller 28 movable in rotation relative to the carrier 24. The roller 28 can be positioned at one end of the carrier 24. The carrier 24 is able to tension the transmission element 12 via the roller. In other words, the roller 28 is mounted movable (free) in rotation on the carrier 24 and can be stressed against the transmission element 12. The connection between the carrier 24 and the roller 28 can be materialized by a bearing centered on an axis of rotation 29. The pulley forming the roller 28 can be smooth or notched.

[0047] The movement of the carrier 24 forces the roller 28 against the transmission element 12, which makes it possible to tension the transmission element 12. The roller 28 movable in rotation on the carrier 24 makes it possible to stress the transmission element 12 while limiting friction against the transmission element 12. The carrier 24 and the roller 28 make it possible to tension the transmission element 12, without slowing down the transmission of movement from one pulley 14, 16 to the other.

[0048] Applying tension against the transmission element 12 through the roller 28 (i.e., a third pulley) allows the axes of rotation of the driving and driven pulleys to be kept fixed. The device can therefore be used when the pulley transmission interfaces with other elements of the environment that cannot be moved (such as a transmission downstream of the driven pulley). In addition, the invention makes it possible to act on the slack strand of the transmission element 12 (unlike the device of US6030305 where the action is on both strands by moving the pulleys apart from each other). For example, for a transmission element 12 in the form of a toothed belt or a chain, the device does not interfere with the strand that transmits the load and therefore the dynamics are better. The pre-tension / maximum transmitted torque ratio is also better.

[0049] The elastic member 20 may be on the carrier 24. The elastic member 20 may be worn by the carrier 24. In other words, the elastic member 20 may be assembled, fixed to the carrier 24. The elastic member 20 is then driven in movement with the carrier 24. The entire elastic member 20 is driven in movement with the carrier 24. The elastic member 20 is changed position during operation of the device during movement of the carrier 24. The entire elastic member 20 is changed position during operation of the device during movement of the carrier 24. The translational movement of the carrier 24 according to figures 1-3 drives the elastic member 20 in translation. In the example of figures 1-3, the elastic member 20 can be a helical spring embedded at one end in the carrier 24. At its other end, the elastic member 20 can be stressed by the adjustment means 18.The rotational movement of the carrier 24 around its axis of rotation 26 according to figures 4-6 drives the elastic member 20 in rotation around the axis of rotation 26. In the example of figures 4-6, the elastic member 20 is a blade embedded at its end 201 in the carrier 24. The elastic member 20 is cantilevered on the carrier 24. At its other end 202, the elastic member 20 is stressed by the adjustment means 18. Thus the embedding point, of fixing of the elastic member 20 is changed position during the operation of the device during the movement of the carrier 24.

[0050] According to the first stroke of the adjustment means 18, the carrier 24 (in its movement) is able to tension the transmission element 12 with the first tension by the elastic member 20. The elastic member 20 urges the carrier 24 to tension the transmission element 12. The adjustment means 18 does not directly urge the carrier 24, but urges the elastic member 20 which in turn urges the carrier 24. Then, according to the second stroke of the adjustment means 18, the carrier 24 (in its movement) is able to tension the transmission element 12 with a second additional tension by the adjustment means 18. The adjustment means 18 urges the carrier to tension the transmission element 12.

[0051] According to the figures, the deformation of the elastic member 20 is limited at the stop. The deformation of the elastic member may be less than its maximum deformation. The deformation of the elastic member 20 may be limited at the stop in several ways. The first stroke of the adjustment means 18 stressing the adjustment member may be limited at the stop. The adjustment means 18 is movable over a certain stroke before coming to the stop. On this first stroke, the adjustment means 18 deforms the elastic member 20 and at the end of this first stroke, the adjustment means 18 comes to the stop. At the end of the first stroke, the elastic member 20 is deformed in a limited manner. Also, the elastic member 20 may itself come to the stop, which limits its deformation. The deformation of the elastic member 20 stops when the adjustment means 18 and / or the elastic member 20 are at the stop.

[0052] Preferably, the deformation of the elastic member 20 can be limited in abutment by the wearer. The deformation of the elastic member 20 can be limited in abutment by the adjustment means 18 coming into abutment 30 against the wearer 24 at the end of the first stroke or by the elastic member 20 coming into abutment 30 against the wearer. The deformation of the elastic member 20 can be limited by limiting the first stroke of the adjustment means 18 to abutment 30 by the carrier 24. The first stroke of the adjustment means 18 can be limited to abutment by the adjustment means 18 coming into abutment against the carrier 24. The first stroke of the adjustment means 18 can be limited to abutment by the elastic member 20 coming into abutment against the carrier 24. At the end of the first stroke of the adjustment means 18, the adjustment member 18 and / or the elastic member 20 are in abutment, in contact against the carrier 24.

[0053] The operation of the device 10 - and more generally of the drive system 11 - and a tensioning method according to the invention can occur as follows. Any description of the device and its operation can be transposed to the tensioning method, and vice versa.

[0054] According to the first stroke 13 of the adjustment means 18, the carrier 24 of the device is able to tension the transmission element 12 with the first tension by the elastic member 20 whose deformation is limited. The adjustment means 18 urges the elastic member 20 into deformation in a limited manner by abutment 30 against the carrier 24. During the first stroke of the adjustment means 18, the tension in the transmission element is adjusted by the deformation of the elastic member 20. The deformation of the elastic member 20, which is carried by the carrier 24, drives the carrier 24 in movement, the carrier 24 urging the transmission element 12 into tension - by the roller 28 if necessary. The adjustment of the adjustment means 18 (such as a screw) makes it possible to deform the elastic member 20 (such as a spring) which will transmit this force to the carrier 24 (for example by means of the connection 201), and therefore increase the tension in the transmission element 12.According to Figures 1-3, the carrier 24 has a translational movement. According to Figures 4-6, the carrier 24 has a rotational movement around the axis of rotation 26. The stress on the transmission element 12 by the carrier 24 puts the transmission element 12 under tension with a first tension. In Figure 2 (applicable to Figure 5), the position of the transmission element is seen in dotted lines corresponding to the position of Figure 1.

[0055] Beyond the first stroke, and according to the second stroke 15 of the adjustment means 18, the carrier 24 of the device is able to tension the transmission element 12 with the second additional tension by the adjustment means 18 urging the carrier 24. The adjustment means 18 is in abutment and the elastic member 20 is limited in deformation by the abutment 30. The adjustment means 18 and the elastic member are in abutment, in contact against the carrier 24. During the second stroke 15, the adjustment means 18 urges the carrier 24 against the transmission element 12. In particular, the carrier 24 is urged by the adjustment means 18 and no longer only by the elastic member 20 limited in deformation. According to figures 1-3, the carrier 24 has a translational movement. According to figures 4-6, the carrier 24 has a rotational movement around the axis of rotation 26.The adjustment means 18 is in contact with the carrier 24 at the stop 30 - directly or indirectly with the elastic member 20 between the adjustment means 18 and the stop 30. The adjustment means 18 is in movement on the second stroke depending on the second tension to be applied in the transmission element 12. During the second stroke, the elastic member 20 is blocked in deformation and is driven in movement with the carrier 24. In Figure 3 (applicable to Figure 6), the positions of the transmission element are seen in dotted lines corresponding to the positions of Figures 1 and 2.

[0056] The tensioning of the transmission element 12 is therefore carried out in a two-phase sequence or modes. This two-phase sequence of the tensioning may correspond to an adjustment of the tensioning (or obtaining a pre-tension). This adjustment may take place before use of the drive system 11 or during a maintenance operation. According to the first phase, the first tension is communicated to the transmission element 12 by deformation of the elastic member 20. At the end of the first phase, the deformation of the elastic member 20 is limited, at the stop. In this first phase, the tension of the transmission element is force-controlled thanks to the deformation of the elastic member. The elastic member is dimensioned so as to apply a (relatively) stable (and known) force (therefore tension) on the transmission element 12 when it is deformed to its limit.Then according to the second phase, the second tension - additional to the first tension - is communicated to the transmission element 12 by the adjustment means 18 which continues its travel while the elastic member is inhibited. During the second phase, the device is able to directly tension the transmission element 12. The travel of the adjustment element 18 is continued as a function of the second tension to be applied in addition in the transmission element 12. In this second phase, the tension of the transmission element 12 is controlled in displacement by the modification of a point of passage of the transmission element. The tension can be controlled by displacement (or movement) of the device 10 (if necessary, by movement of the carrier 24 requested by the adjustment means 18). This displacement communicated by the adjustment means is calculated as a function of the relationship between the tension of the transmission element 12 and the resulting tension.The movement of the device 10 makes it possible in particular to move the elastic member 20, without modifying its deformation.

[0057] In other words, by adjusting the adjustment means 18 (such as a screw), the elastic member which will generate the first stroke 13 of the transmission element 24 is constrained, up to the stop of the elastic member. At this precise moment, the tension of the transmission element is known by knowing the characteristics of the elastic member (such as the force constant of a spring kx). Then, it is possible to increase the tension of the transmission element up to the desired tension by operating the second stroke 15 of a fixed displacement (for example by screwing the screw according to a fixed displacement). The second stroke 15 is for example a number of turns of the screw possibly not an integer, giving the desired displacement, linked by the characteristics of the screw, such as the screw pitch.

[0058] The device 10 makes it possible to adapt the tensioning sequence to the properties of the transmission element 12. The first phase tensions the transmission element 12 to a known value, independently of deviations due to production tolerances of the transmission element 12 or other surrounding mechanical components. The second phase finalizes the tension of the transmission element 12 by adding a known displacement to the initial position obtained during the first phase.

[0059] The drive system 11 may comprise a casing 22 (visible in Figures 4-6 but also applicable to Figures 1-3). The transmission element 12 and the device 10 may be at least partly in the casing 22. This makes it possible to protect them (for example against dust, shocks, etc.). The transmission element 12 may be at least partly in the casing 22. It is conceivable that the transmission element 12 is completely in the casing 22 or partially in the casing 22 at the level of the device 10. The device 10 may also be at least partly in the casing 22. For example, the adjustment means 18 may extend between the outside and the inside of the casing 22. The adjustment means 18 may also be in the casing 22, being accessible from the outside of the casing 22. The casing 22 also makes it possible to support the constituent elements of the invention.

[0060] The casing 22 may include a sight glass (not visible in the figures) intended to control the first stroke and / or the second stroke of the adjustment means 18. This makes it possible to ensure reliable tension by means of visual control and without a specific tool for measuring force, torque or tension. The sight glass may make it possible to follow the adjustment means 18 over its first stroke. The sight glass makes it possible to identify when the adjustment means 18 is in abutment 30 - possibly against the carrier 24 if necessary. The sight glass makes it possible to identify when the adjustment means 18 - and potentially the elastic member - is in contact with the carrier 24. This makes it possible to detect that the tensioning is at the end of the first phase. The sight glass also makes it possible to follow the adjustment means 18 over its second stroke. The second stroke may also be determined by monitoring the actuation of the adjustment means 18.The second stroke can be determined by an additional movement of the adjustment means 18. For example, in the form of a screw, an additional rotation of the adjustment member 18 by a certain angle makes it possible to determine the second stroke and therefore the second additional tension. The sight glass can be covered by a part making it possible to close the casing 22. The part can be transparent (to visually follow the tensioning) or be opaque (once the tensioning has been carried out). The end of the first stroke can be communicated to the operator by other means such as an electronic element by closing a circuit at the contact.

[0061] During operation with a nominal load in the drive system 11, the device 10 puts the transmission element 12 under tension; the adjustment means imposes the tension in the transmission element with the elastic member 20 which is limited in deformation. The elastic member 20 is in abutment 30 - possibly against the carrier 24 - and its effect is inhibited. When the load in the drive system 11 increases during operation, an elongation of the transmission element may occur causing a drop in the tension in the transmission element 12. The force applied by the transmission element 12 to the device 10 may become less than the force required to maintain the elastic member 20 at its limited deformation. There is then a risk that the transmission element will move out of its path or no longer transmit the power correctly. The elastic member 20 then makes it possible to compensate for the elongation of the transmission element 12.The carrier 24 - and more generally, the device 10 - is capable of maintaining a tension in the transmission element by the elastic member 20. The elastic member 20 carried by the carrier 24 is moved by the carrier 24 during the second stroke of the adjustment member 18, allowing the elastic member 20 to again apply a tension in the transmission element 12 which undergoes elongation. The system is capable of being implemented in an application which operates at a nominal voltage (highly used) which is very different and lower than the maximum voltage (rare case).

[0062] After tensioning the adjustment means 18 over both strokes, the proposed device and system thus offer a dual mode of use, one for nominal load cases and the other for high load cases. In normal operating mode, under nominal load, the device and system operate as a fixed tensioning mechanism in operation, which is desirable to avoid vibrations. In this mode, the device is as rigid as possible. In the "anti-jump" operating mode, under high load cases, the device and system transform into a tensioning system with an elastic member. In this mode, the device can take up a significant elongation of the transmission element thanks to the elastic member.The two combined modes allow a good compromise between three conflicting requirements, namely: operating with as high a rigidity as possible to avoid vibrations linked to an alternating deformation cycle between the transmission element and the elastic member; allowing maximum elongation of the transmission element in order to be able to transmit maximum torque without transmission element jump (i.e. without loss of mesh or without the appearance of excessive slip); having a pre-tension (during adjustment, at the end of the two phases of tensioning) as low as possible to reduce friction in the entire system, and the forces on the transmission (bearings for example).

[0063] The device and system are advantageous in that it avoids applying a high preload in the transmission element to cope with any rare risk of loosening in case of higher load. It also avoids higher static friction and higher load on the pulleys and bearings. Thanks to the invention, it is possible to tension (pretension) the transmission element with a lower tension, corresponding to the nominal case with normal load, while still being able to tension the transmission element in cases of high load in order to ensure correct operation of the transmission element. Furthermore, the device and system make it possible to solve the problem of measuring the tension for adjustment (tensioning) - the elastic member (such as a spring) helping to make the correct adjustment.

[0064] During transmission by a chain or belt type transmission element, a pre-tension T0 can be applied, which can be zero or not (at zero torque). In operation, a tension (proportional to the torque) is added to one of the strands of the transmission element and is removed from the other strand. A tension Ts can be obtained which is applied in the least tense strand (or slack strand) and a tension Th can be obtained which is applied in the most tense strand. When the torque in the transmission becomes too high, the tension in the slack strand Ts becomes zero, which can lead to a transmission fault (for example, a tooth jumping in the case of a chain or a toothed belt, particularly in fixed tensioner type devices). This transmission fault is resolved with the device, thanks to the elastic member 20 which can take effect and take up the slack while leaving tension. This is illustrated schematically in Figure 7.Figure 7 shows the elongation E of the transmission element 12 on the abscissa as a function of the tension Ts on the ordinate (of the slack strand). Curve 32 corresponds to the stiffness slope of a transmission element. The tension in the slack strand of the transmission element decreases in the event of an increase in its elongation. Curve 32 on the ordinate axis corresponds to zero torque. Following curve 32, by increasing the torque, curve 32 reaches the abscissa axis E: the taut strand becomes more taut and the slack strand softens more to the point that the tension becomes zero in the slack strand when the abscissa axis E is reached. Curve 34 shows the normal operating mode 36 of the device 10 and system 11. As the load increases in the system, the transmission element 12 applies a reaction force against the device 10 which decreases.Curve 38 shows that beyond a certain elongation 40 (or in other words, a certain elongation or elongation threshold) of the transmission element, the device 10 switches to the anti-jump mode 42 which is controlled by the stiffness of the elastic member 20. The device is capable of maintaining the transmission element 12 in tension during the elongation of the transmission element, the elastic member 20 compensating for the elongation of the transmission element.

[0065] According to Figure 7, in comparison with curves 32 and 34 / 38, it is possible to apply a lower tension in the transmission element for normal operation of the system (normal mode, curve 34), the elastic member 20 making it possible to apply a tension compensating for the elongation of the transmission element in the event of elongation beyond a certain threshold (anti-jump mode, curve 38).

[0066] Figure 8 shows the tensioning. Figure 8 shows the variation of the pretension T0 as a function of the setting S of the adjustment means 18. Figure 8 shows the behavior of the device 10 and of the system 11 during tensioning. According to curve 44, and according to the first stroke 13, the slope depends mainly on the stiffness of the elastic member 20 and the stiffness of the transmission element 12 seen from the device 10. Point 48 corresponds to the point of contact at the end (i.e. to the limit of the deformation of the elastic member). According to curve 46, and according to the second stroke 15, the slope depends mainly on the stiffness of the transmission element 12 seen from the device 10. Point 50 corresponds to the pretensioning of the device, or in other words, to the nominal adjustment point of the device.

[0067] The device 10 uses an elastic member (of the spring type) whose stiffness and initial length are controlled. The device 10 works at an ideal operating point, minimizing the tension of the transmission element for a maximum transmitted torque. The device uses the known deformation (on the first stroke) and the known stiffness to obtain this desired tension in the first stroke in addition to a second tension due to the second stroke. According to the invention, a first stroke is carried out up to the limit deformation (for example by contact with a stop), after which, a second stroke is applied (for example of known length). Under normal conditions, the device is stiffer and the parasitic vibrations are less in comparison with the prior art and in particular the document US6030305.

[0068] The device 10 makes it possible to increase the service life of the transmission system 11 while being light, simple, compact and inexpensive. The device 10 is a simple device for tensioning a system with highly variable torque efficiently. The device has the advantages (independent of each other or taken in combination) of having anti-jump operation and being easy to adjust.

[0069] The invention also relates to any apparatus comprising the drive system and in which a transmission element is implemented and which is subjected to tensioning. The invention relates in particular to a vehicle comprising the drive system. For example, the vehicle may be a bicycle or a motorcycle. The bicycle or motorcycle may comprise the transmission element 12 which may be a belt or a transmission chain between, on the one hand, a crankset and / or a powertrain and, on the other hand, a wheel. The advantages mentioned for the device (light, simple, compact and inexpensive device) are particularly appropriate in the context of a vehicle where such advantages are constantly sought. The present invention has been described in relation to specific embodiments, which have a purely illustrative value and should not be considered as limiting.Generally speaking, it will be obvious to a person skilled in the art that the present invention is not limited to the examples illustrated and / or described above.

Claims

Claims 1. Device (10) for tensioning a deformable transmission element comprising A means (18) for adjusting the tension in the transmission element, An elastic member (20), The adjustment means (18) being able to be movable: According to a first stroke (13), the device being able to tension the transmission element (12) with a first tension by the elastic member (20) whose deformation is limited, and, beyond the first stroke (13), according to a second stroke (15), the device being able to tension the transmission element (12) with a second additional tension by the adjustment means (18), the second stroke being a function of the second tension to be applied in the transmission element (12).

2. Device (10) according to the preceding claim, in which, during the movement of the adjustment means (18) on the second stroke, the elastic member (20) is able to be maintained at its limited deformation.

3. Device (10) according to one of the preceding claims, further comprising a carrier (24), the device being capable of tensioning the transmission element (12) via the carrier.

4. Device (10) according to the preceding claim, comprising a roller (28) movable in rotation relative to the carrier (24), the carrier being capable of tensioning the transmission element (12) via the roller.

5. Device (10) according to one of claims 3 or 4, in which the elastic member (20) is on the carrier (24).

6. Device (10) according to the preceding claim, in which the elastic member (20) is changed position during operation of the device during movement of the wearer (24).

7. Device (10) according to claim 5 or 6, in which the point of attachment of the elastic member (20) to the wearer (24) is changed position during operation of the device during movement of the wearer (24).

8. Device (10) according to one of claims 3 to 7, in which the deformation of the elastic member (20) is limited in abutment.

9. Device (10) according to one of claims 3 to 8, in which the deformation of the elastic member (20) is limited in abutment by the wearer.

10. Device (10) according to one of claims 3 to 9, in which the deformation of the elastic member (20) is limited in abutment by the adjustment means (18) coming into abutment against the carrier (24) at the end of the first stroke or by the elastic member (20) coming into abutment against the carrier.

11. Device (10) according to one of claims 3 to 10, in which According to the first stroke (13) of the adjustment means, the carrier (24) of the device is able to tension the transmission element (12) with the first tension by the elastic member (20) whose deformation is limited, the adjustment means (18) urging the elastic member (20) into deformation in a limited manner by abutment (30) against the carrier, and, beyond the first stroke, According to the second stroke (15) of the adjustment means, the carrier (24) of the device is able to tension the transmission element (12) with the second additional tension by the adjustment means (18) urging the carrier, the second stroke being a function of the second tension to be applied in the transmission element.

12. Device (10) according to one of the preceding claims, in which the elastic member (20) is chosen from the group comprising a leaf spring, a helical spring, a spiral torsion spring, a stud made of elastic material, a structural part designed to provide the appropriate stiffness for the tension to be placed in the transmission element (12).

13. Device (10) according to one of the preceding claims, in which the adjustment means (18) is a screw or an eccentric.

14. Drive system (11), comprising A deformable transmission element (12), The device (10) according to one of the preceding claims, the device being capable of tensioning the transmission element (12).

15. System (11) according to the preceding claim, further comprising a casing (22), the transmission element (12) and the device (10) being at least partly in the casing, the adjustment means being accessible from outside the casing, the casing comprising a viewport intended to control the first stroke (13) and / or the second stroke (15) of the adjustment means (18).

16. System (11) according to claim 14 or 15, in which the device (10) is further capable of tensioning the transmission element (12) during elongation of the transmission element during operation, the elastic member (20) compensating for the elongation of the transmission element.

17. A vehicle with the drive system (11) according to one of claims 14 to 16.

18. The vehicle according to the preceding claim, the vehicle being a bicycle or a motorcycle.

19. Method for tensioning a transmission element in a drive system (11), the method comprising The provision of a system (11) according to one of claims 14 to 16, The tensioning of the transmission element (12) by the device (10), comprising • According to the first stroke (13) of the adjustment means, the tensioning of the transmission element (12) with a first tension by the elastic member (20) whose deformation is limited, then, beyond the first stroke, • According to the second stroke (15) of the adjustment means, the tensioning of the transmission element (12) with a second additional tension by the adjustment means (18), the second stroke being a function of the second tension to be applied in the transmission element.

20. Method according to the preceding claim, the device (10) further comprising a carrier (24), the device being capable of tensioning the transmission element (12) via the carrier, the deformation of the elastic member (20) is limited in abutment by the adjustment means (18) coming into abutment against the carrier (24) at the end of the first stroke or by the elastic member (20) coming into abutment against the carrier.

21. Method according to one of claims 19 or 20, the system (11) further comprising a casing (22), the transmission element (12) and the device (10) being at least partly in the casing, the adjustment means (18) being accessible from outside the casing, the casing comprising a sight glass, the method comprising monitoring the first stroke and / or the second stroke of the adjustment means (18) through the sight glass.

22. Method according to one of claims 19 to 21, further comprising tensioning the transmission element (12) by the elastic member (20) of the device during an elongation of the transmission element during operation, the elastic member (20) compensating for the elongation of the transmission element.

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