Cycle gear-shift system

Abstract

The invention relates to a gear-shift system (100) for a chain (10) comprising a shaft (102), a first toothed chainwheel (104) inscribed in a working plane (P), secured to said shaft (102) and meshing with the chain, at least one other toothed chainwheel (106a-d) divided into toothed angular sectors (108a-e), each of which is movable in translation between a rest position in which said toothed angular sector (108a-e) is offset with respect to the working plane (P) and an active position in which said toothed angular sector (108a-e) is in the working plane (P), and a shifting system which moves each toothed angular sector (108a-e) from the rest position to the active position and vice versa.

Description

[0001] GEAR CHANGE SYSTEM FOR CYCLE

[0002] TECHNICAL FIELD

[0003] The present invention relates to a gear change system in particular for a cycle and a cycle comprising such a gear change system.

[0004] PREVIOUS STATE OF THE ART

[0005] A bicycle typically consists of a chain mounted between a chainring at the front and a sprocket at the rear. To assist the cyclist, the bicycle typically includes a gear-shifting system with a rear derailleur and a front derailleur. Each derailleur allows the cyclist to select a chainring and sprocket suited to the desired effort level.

[0006] To this end, the cycle has several chainrings (which, in this document, are called toothed discs) at the bottom bracket and sprockets at the rear wheel, arranged coaxially next to each other. Each derailleur ensures the lateral movement of the chain from one chainring, or sprocket, to the adjacent chainring, or sprocket.

[0007] Even if such derailleurs perform satisfactorily, they cause chain flex during lateral movement, generating stress that can lead to creaking, or even unexpected and destructive derailments of both the derailleur and the chain. These problems are particularly noticeable during gear changes under load (i.e., when force is applied to the crankset and chain during a gear change).

[0008] DESCRIPTION OF THE INVENTION

[0009] One object of the present invention is to provide a gear-changing system, particularly for cycles, without torque interruption and without lateral chain movement. To this end, a gear-changing system for a chain is proposed, said gear-changing system comprising:

[0010] - a rotating shaft that pivots around a pedaling axis,

[0011] - a first toothed disc inscribed in a working plane, integral with said shaft and intended to mesh with the chain, - at least one other toothed disc divided into at least two toothed angular sectors, where each toothed angular sector is movable in translation between a rest position in which said toothed angular sector is offset from the working plane and an active position in which said toothed angular sector is in the working plane, and

[0012] - a displacement system arranged to move each toothed angular sector from the rest position to the active position and vice versa.

[0013] Advantageously, for each other toothed disc, the displacement system comprises a translationally movable gear-shifting arm, a rotationally movable cam having a cam track where a proximal end of the gear-shifting arm is guided by the cam track, and each toothed angular sector of said other toothed disc comprises first actuation means that cooperate with a distal end of the gear-shifting arm to move said toothed angular sector from the rest position to the active position and second actuation means that cooperate with the distal end of the gear-shifting arm to move said toothed angular sector from the active position to the rest position.

[0014] Advantageously, for each toothed angular sector, the gear change system includes locking means arranged to lock said toothed angular sector alternately in the active position and the rest position.

[0015] Advantageously, the gear change system includes a cage attached to the shaft, divided into sectors in which toothed angular sectors are mounted, and for each sector, the cage includes first guiding means cooperating with second guiding means of the toothed angular sectors to achieve a sliding connection.

[0016] Advantageously, for each toothed angular sector, the locking means consist of a ball mounted on a spring in a housing of the toothed angular sector and for each position, a recess in the cage into which the ball is inserted in the corresponding position.

[0017] Advantageously, the system includes a cam with an indexing notch and a groove serving as an extreme stop.

[0018] Advantageously, the system includes a third roller that opens a chain engagement zone, allowing for gear changes in all situations. Advantageously, the system incorporates ad hoc conjugate zones between the toothed angular sectors, enabling the force between the bottom bracket axle and the chain to be transmitted directly from one toothed disc to another.

[0019] The invention also proposes a cycle comprising a speed change system according to one of the previous variants and a chain mounted in the work surface and engaging with the first toothed disc where the transition from the active position to the rest position and vice versa takes place in an angular sector delimited between two strands of the chain where the chain does not engage with the first toothed disc.

[0020] Advantageously, the cycle includes a tensioning system arranged to put the chain under tension.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which:

[0023] [Fig. 1] is a perspective view of a cycle drive system comprising a gear-changing system according to the invention,

[0024] [Fig. 2] is a side view of the drive system of Fig. 1 without the cover,

[0025] [Fig. 3] is a perspective view of the gear shifting system according to the invention, [Fig. 4] is a perspective view of the gear shifting system according to the invention, [Fig. 5] is a perspective view of a detail of the gear shifting system according to the invention,

[0026] [Fig. 6] is a perspective view of the detail in Fig. 5 viewed from another angle,

[0027] [Fig. 7] is a perspective view of a toothed slide implemented in the gear-changing system according to the invention,

[0028] [Fig. 8] is a perspective view of a detail of the gear-changing system according to the invention,

[0029] [Fig. 9] is a side view of a first cam implemented in the gear-changing system according to the invention,

[0030] [Fig. 10] is a side view of a second cam implemented in the gear-changing system according to the invention,

[0031] [Fig. 11] is a side view of a third cam implemented in the gear-changing system according to the invention, [Fig. 12] is a side view of a fourth cam implemented in the gear-changing system according to the invention,

[0032] [Fig. 13] is a perspective view of a guidance system for a gear shift arm,

[0033] [Fig. 14] is a cross-section by a plane perpendicular to a pedaling axis of the gear-changing system according to the invention,

[0034] [Fig. 15] is a perspective view of one embodiment of a gear-changing system.

[0035] DETAILED EXPLANATION OF IMPLEMENTATION METHODS

[0036] Fig. 1 shows a gear-changing system 100 according to the invention, implemented, for example, in a bicycle. Such a gear-changing system 100 can be implemented in all types of systems comprising gears driven in rotation by a driving force (engine, muscle) and driving a chain, or driven by a chain. The gear-changing system 100 is particularly well-suited to vehicles with internal combustion engines, electric motors, or muscle power, such as bicycles, electric bicycles, etc.

[0037] The invention will be described more particularly in the case of a cycle, but it applies in the same way to other systems where it can be implemented.

[0038] Fig. 2 shows the gear-changing system 100 without a protective cover. A bicycle typically consists of a frame on which a front wheel and a rear wheel are mounted as rotating parts. Arrow F indicates the direction of travel of the bicycle. The bicycle has a rear hub 12 in which a rear axle is mounted, which is integral with the rear wheel. The hub also carries a rear sprocket onto which a chain 10 meshes. In the embodiment of the invention presented here, the chain 10 is enclosed in a chain guard 14.

[0039] Similarly, the gear-shifting system 100 comprises a frame 16 which is fixed to the bicycle frame, for example, by screws, and which here takes the form of a protective casing in which the gear-shifting system 100 mechanism is enclosed. The bicycle has a shaft 102 mounted to rotate freely on the frame around a pedaling axle X. The shaft 102 is equipped with two cranks 18, each fitted with a pedal 20. Conventionally, actuating the pedals 20 drives the cranks 18, which in turn rotates the shaft 102. The shaft 102 can also be the shaft of a motor, for example, an electric motor. In the embodiment of the invention presented here, the gear-shifting system 100 is installed at the chainrings 104 and 106a-d, but it can also be installed at the sprockets, either as a complement or as a replacement.Thus, according to a particular arrangement, the gear change system 11 can be set up at the sprockets using an additional system to synchronize the gear changes at the crankset, with another gear change located on an intermediate shaft or on a rear wheel axle.

[0040] In the following description, a chainring, whether segmented or not, is referred to as a "toothed disc" when it is at the pedals, and as a sprocket when it is at the rear or coupled to a secondary shaft in a gearbox interposed between the crankset and the rear wheel. Figures 3 and 4 show the gear-shifting system 100 from two opposite angles. The gear-shifting system 100 thus comprises the shaft 102 and a first toothed disc 104. The first toothed disc 104 is inscribed in a working plane P that is perpendicular to the pedaling axis X. The working plane P is the plane in which the chain 10 moves.

[0041] The first toothed disc 104 is fixed to the shaft 102 and meshes with the chain 10. Thus, the rotation of the shaft 102 causes the chain to move, which in turn drives the rotating sprocket and, consequently, the rear wheel. In a particular arrangement, the sprocket is equipped with a freewheel mechanism.

[0042] The gear change system 100 also includes at least one other toothed disc 106a-d, here four in number, for a five-ring cycle. Each other toothed disc 106a-d has a diameter larger than the diameter of the first toothed disc 104, and the diameters of the other toothed discs 106a-d are all different so that toothed discs 104 and 106a-d are arranged one inside the other in a nested arrangement.

[0043] Each other toothed disc 106a-d is divided into at least two toothed angular sectors 108a-e, here five in number. Each toothed angular sector 108a-e has teeth 109 on its periphery which cooperate with the chain 10. Preferably, all the toothed angular sectors 108a-e have the same angular extent here of 72° and the same number of teeth.

[0044] Each toothed angular sector 108a-e is centered on the pedaling axis X and is connected to the shaft 102 so as to rotate with it. There are thus n*N toothed angular sectors 108a-e, where n is the number of toothed angular sectors 108a-e per other toothed disk 106a-d and N is the number of other toothed disks 106a-d. Preferably, there is the same number of toothed angular sectors 108a-e for each other toothed disk 106a-d, and the toothed angular sectors 108a-e are aligned concentrically around the pedaling axis X (except during the lateral movement of each angular sector).

[0045] Each toothed angular sector 108a-e is translationally movable between a rest position in which the toothed angular sector 108a-e is offset from the working plane P and an active position (106c, Fig. 5) in which the toothed angular sector 108a-e is in the working plane P. The movement from the rest position to the active position is shown here by the arrows D in Figs. 3 and 4. The direction of the translation is parallel to the pedaling axis X.

[0046] In the rest position, the toothed angular sector 108a-e is outside the working plane P and the teeth 109 do not mesh with the chain 10. In the active position, the toothed angular sector 108a-e is in the working plane P and the teeth 109 mesh with the chain 10.

[0047] The gear change system 100 also includes a displacement system 150 that moves each toothed angular sector 108a-e from the rest position to the active position and vice versa. Upon reaching the active position, the toothed angular sector 108a-e will then mesh (in its rotation) with the chain 10. To facilitate the entry of the chain 10 onto the toothed angular sector 108a-e, at least the first tooth of said toothed angular sector 108a-e may have a different profile (more pointed or more rounded or beveled or grooved, for example).

[0048] Thus, when the cycle operator wants to change toothed discs 104, 106a-d, that is, to change speeds, they activate the displacement system 150, which will successively move, within the chain space, each toothed angular sector 108a-e of the toothed disc 106a-d to be moved. Depending on the case, these toothed angular sectors 108a-e will move from the rest position to the active position or vice versa. The operator will actuate the displacement system 150 as many times as necessary in either direction to position the desired toothed disc 104, 106a-d in the meshing position with the chain 10.

[0049] From the first toothed disc 104, the displacement system 150 gradually moves the other toothed discs 106a-d from the rest position to the active position by going from the smallest diameters to the largest diameters, and vice versa for the passage from the active position to the rest position.

[0050] Since the gear change occurs at the level of the chain 10, the chain is not bent, the drawbacks of prior art are avoided, and the effort required from the driver remains constant. The drive system 150 is actuated, for example, from the handlebars by operating a twist grip or other means via cables 22a-b that connect to the drive system 150. Alternatively, the drive system 150 can also be electrically actuated by an automated system or by a user.

[0051] Figures 7 to 14 show a particular embodiment of the 150 displacement system.

[0052] Here, there is an ascending cable 22a that ensures the transition from the rest position to the active position and a descending cable 22b that ensures the transition from the active position to the rest position. For each other toothed disc 106a-d, the shifting system 150 includes a gear shift arm 152. Each gear shift arm 152 is mounted to move in translation, here parallel to the pedaling axis X. To this end, each gear shift arm 152 is mounted to slide within a fixed tunnel 17, which is integrated here into the frame 16.

[0053] For each other toothed disc 106a-d, the displacement system 150 also includes a cam 154 which is mounted to rotate freely about an actuation axis X' which is here perpendicular to the pedaling axis X. The cams 154 are mounted fixed and coaxially on a shaft 153 which is mounted on the frame 16 and which is rotatable about the actuation axis X'.

[0054] The cables 22a-b are fixed to the shaft 153 in such a way that pulling one cable 22a causes the shaft 153 to rotate in a first direction corresponding to the passage from the rest position to the active position, and in such a way that pulling the other cable 22b causes the shaft 153 to rotate in a second direction corresponding to the passage from the active position to the rest position.

[0055] Each cam 154 has a cam track 154a. In the embodiment of the invention presented here, there is a single cam 154 for two of the other toothed discs 106a-d, and a cam track 154a is formed on each face of said same cam 154. According to an embodiment not shown, the cam 154 may be provided with notches allowing precise indexing of each speed. Said notches then cooperate with an indexing finger actuated by a spring.

[0056] Each gear shift arm 152 has a proximal end and a distal end. The proximal end of the gear shift arm 152 is guided by the cam track 154a and here takes the form of a movable bearing rotating about an axis parallel to the actuation axis X'.

[0057] Each toothed angular sector 108a-e of each other toothed disc 106a-d has on a cylindrical face coaxial with the pedaling axis X, first actuation means 156a and second actuation means 156b. Here, the actuation means 156a-b take the form of a boss on said toothed angular sector 108a-e.

[0058] The distal end of the gear-shifting arm 152 cooperates with the actuation means 156a-b to move the relevant toothed angular sector 108a-e, where the first actuation means 156a ensure the transition from the rest position to the active position and the second actuation means 156b ensure the transition from the active position to the rest position. The distal end also takes the form of a movable bearing rotating about an axis parallel to the actuation axis X'.

[0059] Thus, when the cam track 154a moves the proximal end (arrow +, Fig. 8, corresponding to arrow D), the distal end moves, and as the toothed angular sector 108a-e rotates, the first actuating means 156a encounter the distal end, and the shape of the first actuating means 156a causes the angular sector 108a-e to move towards the active position. Conversely, when the cam track 154a moves the proximal end (arrow -, Fig. 8), the distal end moves, and as the toothed angular sector 108a-e rotates, the second actuating means 156b encounter the distal end, and the shape of the second actuating means 156b causes the angular sector 108a-e to move towards the rest position.

[0060] As shown in Figs. 9 to 12, each cam track 154a is different so as to trigger the movement of the various gearshift levers 152 in a synchronized manner. The movement of the gearshift arm 152 occurs at the point where the orientation of the cam track 154a changes. The outer circular portion 153a and the inner circular portion 153b correspond to a non-movement of the gearshift arm 152. The intermediate portion 153c between the outer circular portion 153a and the inner circular portion 153b corresponds to the portion of the cam track 154a that moves the gearshift arm 152 in one direction or the other depending on the direction of rotation of the cam 154.

[0061] In the embodiment of the invention shown in Fig. 8, when the gear shift arm 152 is moved in the + direction, the distal end rolls against the track 156c until the first actuation means 156a arrive, which moves the toothed angular sector 108a-e. By successive passage of the different toothed angular sectors 108a-e constituting another toothed disk 106a-d, said toothed angular sectors 108a-e will position themselves one after the other in the active position or in the rest position.

[0062] Each actuation means 156a-b here takes the form of a ramp. To ensure locking in the rest position and in the active position, for each toothed angular sector 108a-e, the gear change system 100 includes locking means 170. These locking means 170 are arranged so as to lock the toothed angular sector 108a-e alternately in the active position and the rest position while allowing the release of the toothed angular sector 108a-e when reverse movement is desired.

[0063] To ensure proper guidance and alignment of the toothed angular sectors 108a-e, the gear change system 100 includes a cage 160 which is fixed to the shaft 102. The cage 160 is divided into sectors 160a-e, and in each sector 160a-e, the toothed angular sectors 108a-e of the same rank of the other toothed discs 106a-d are mounted to slide. Thus, in each sector 160a-e, a toothed angular sector 108a-e of each of the other toothed discs 106a-d is arranged, and since the cage 160 is fixed to the shaft 102, the rotation of the latter causes the rotation of the toothed angular sectors 108a-e. For each sector 160a-e, the cage 160 includes, for each toothed angular sector 108a-e arranged in said sector 160a-e, first guiding means 162 which cooperate with second guiding means 164 which said toothed angular sectors 108a-e include to make a sliding connection between the guiding means 162 and 164.

[0064] The first guiding means 162 here take the form of ribs and the second guiding means 164 here take the form of grooves in each of which a rib is mounted to slide.

[0065] According to a particular embodiment shown in Fig. 14, the locking means 170 consist of a ball 170a which is movably mounted in a housing 170d of the toothed angular sector 108a-e under consideration. The housing 170d is blind and designed to lock the ball 170a so that it cannot exit the housing 170d, for example by fitting a collar with a diameter smaller than the diameter of the ball 170a at the opening of the housing 170d.

[0066] The locking means 170 also include a spring 170b on which the ball 170a is mounted and which ensures the push of the ball 170a towards the opening of the housing 170d i.e. towards an exit of the ball 170a from the housing 170d.

[0067] For each position, i.e. for the active position and the rest position, the locking means 170 include a recess 170c which is formed on the cage 160 where the recess 170c is arranged so that the ball 170a is inserted into it when the corresponding position is reached by the corresponding toothed angular sector 108a-e. To prevent the toothed angular sectors 108a-e from pushing or pulling on the chain 10 during gear changes, the transition from the active position to the rest position and vice versa takes place in an angular sector 180 around the pedaling axis X which is delimited between the two strands of the chain 10 on the side where the chain 10 does not mesh with the first toothed disc 104 or the other toothed discs 106a-d, i.e. outside the winding zone of the chain 10 (i.e. the chain gap).

[0068] To ensure good tension of the chain 10 when it changes toothed disc 104, 106a-d, the cycle includes a tensioning system 190 which is arranged to put the chain 10 under tension.

[0069] In the embodiment of the invention presented in particular in Figs. 3 and 4, the tensioning system 190 comprises a swing arm 192 which is here fixed to the chassis 16 by means of a screw 194.

[0070] The swing arm l92 is mounted to rotate freely around a tilting axis X” perpendicular to the work plane P.

[0071] Each end of the swing arm l92 is equipped with a toothed roller 196a-b movable in rotation around an axis parallel to the tilting axis X”, where the chain 10 passes between the toothed rollers 196a-b and meshes with each of them.

[0072] The tensioning system 190 also includes a return element 198, here a torsion spring, which forces the lever 192 to rotate in order to tension the chain 10.

[0073] According to a particular arrangement, a third roller 196c allows a free engagement zone of the chain 10 to be opened to allow a gear change in all situations.

[0074] According to another particular arrangement shown in Fig. 15, the system includes a cam 154 having indexing notches 300 and a trench 310 serving as an extreme stop by cooperating with a stop screw.

[0075] According to another particular arrangement, the system includes ad hoc conjugate zones 108f between the toothed angular sectors 108a-e, allowing a force between the bottom bracket axle 102 and the chain 10 to be transmitted directly from one toothed disc to another. In other words, according to this arrangement, the transmission of force occurs radially from the outside to the inside without the forces being transmitted to the chainring arms.

Claims

DEMANDS 1. Gear-changing system (100) for a chain (10) or a belt, said gear-changing system (100) comprising: - a shaft (102) that rotates freely around a pedaling axis (X), - a first toothed disc (104) inscribed in a working plane (P), integral with said shaft (102) and intended to mesh with the chain (10), - at least one other toothed disc (106a-d) divided into at least two toothed angular sectors (108a-e), where each toothed angular sector (108a-e) is movable in translation between a rest position in which said toothed angular sector (108a-e) is offset from the work plane (P) and an active position in which said toothed angular sector (108a-e) is in the work plane (P), and - a displacement system (150) arranged to move each toothed angular sector (108a-e) from the rest position to the active position and vice versa, the gear change system (100) being characterized in that for each other toothed disc (106a-d), the displacement system (150) comprises a gear change arm (152) movable in translation, a cam (154) movable in rotation and having a cam track (154a) where a proximal end of the gear change arm (152) is guided by the cam track (154a),and in that each toothed angular sector (108a-e) of said other toothed disc (106a-d) comprises first actuation means (156a) which cooperate with a distal end of the gear-shifting arm (152) to move said toothed angular sector (108a-e) from the rest position to the active position and second actuation means (156b) which cooperate with the distal end of the gear-shifting arm (152) to move said toothed angular sector (108a-e) from the active position to the rest position.

2. Gear change system (100) according to any one of claims 1 or 2, characterized in that, for each toothed angular sector (108a-e), the gear change system (100) comprises locking means (170) arranged to lock said toothed angular sector (108a-e) alternately in the active position and the rest position.

3. Gear change system (100) according to any one of claims 1 to 3, characterized in that it comprises a cage (160) integral with the shaft (102), divided into sectors (160a-e) in which the toothed angular sectors (108a-e) are mounted, and in that for each sector (160a-e), the cage (160) comprises first guiding means (162) cooperating with second guiding means (164) of the toothed angular sectors (108a-e) to achieve a sliding connection.

4. Gear change system (100) according to claim 4 when it depends on claim 3, characterized in that for each toothed angular sector (108a-e), the locking means (170) consist of a ball (170a) mounted on a spring (170b) in a housing (170d) of the toothed angular sector (108a-e) and for each position, a recess (170c) of the cage (160) into which the ball (170a) is inserted in the corresponding position.

5. Gear change system (100) according to any one of the preceding claims, comprising the cam (154) having an indexing notch (300) and a groove (310) serving as an extreme stop.

6. Gear change system (100) according to any one of the preceding claims, a third roller 196c allowing a free engagement zone of the chain 10 to be opened, to allow a gear change in all situations.

7. Gear shifting system (100) according to any one of the preceding claims, comprising ad hoc conjugate zones (108f) between the toothed angular sectors (108a-e), allowing a force between the bottom bracket axle (102) and the chain (10) to be transmitted directly from one toothed disc to another.

8. Cycle comprising a speed change system (100) according to any one of claims 1 to 8 and a chain (10) mounted in the work plane (P) and meshing with the first toothed disc (104) where the passage from the active position to the rest position and vice versa takes place in an angular sector (180) delimited between two strands of the chain (10) where the chain (10) does not mesh with the first toothed disc (104).

9. Cycle according to claim 9, characterized in that it comprises a tensioning system (190) arranged to put the chain (10) under tension.

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