Transmission wheel and transmission assembly, in particular for a bicycle

Abstract

Disclosed is a transmission wheel (7) which comprises an outer ring gear (17) suitable for engaging with a transmission belt or chain, and an inner ring gear (23), suitable for cooperating with a drive member or with a drive wheel, the outer ring gear (17) comprising a plurality of inner teeth (21) and the inner ring gear (23) comprising a plurality of outer teeth (24). The inner teeth (21) and outer teeth (24) teeth are separated by a space filled with an elastomer material (29) fixed to the outer (17) and inner (23) ring gears.

Description

Wheel and transmission assembly, especially for bicycles [Technical field]

[0001] The present invention lies in the field of mechanics, and more precisely in the field of the transmission of torque supplied by a motor member to a drive wheel. [State of the prior art]

[0002] In many areas the question arises of transmitting the torque supplied by a motor unit to a drive wheel.

[0003] This is particularly the case in the field of bicycles, where the torque supplied by the cyclist and / or by electrical assistance is transmitted to the drive wheel: this transmission is achieved by an assembly comprising a driving transmission wheel, a driven transmission wheel, and a transmission member such as a belt or a chain connecting these transmission wheels together.

[0004] For various reasons, including the mounting of the transmission wheels on the bicycle, deformation of the bicycle frame, and gear changes that may cause the belt or chain to move parallel to the rotation axes of the transmission wheels, misalignment between the transmission wheels may occur.

[0005] This misalignment can be of the parallel type, that is to say that the axes of rotation of the two transmission wheels remain parallel to each other, but the grooves or drive teeth of these two wheels are located in separate parallel planes.

[0006] This misalignment can also be of the angular type, that is to say that the axes of rotation of the two transmission wheels are inclined relative to each other, the grooves or drive teeth of these two wheels then themselves being located in separate planes inclined relative to each other.

[0007] In both cases, the two transmission wheels and the transmission belt or chain are no longer located in a single plane, which causes problems of premature wear due to mechanical friction of the different parts of the transmission assembly, and in particular the teeth or grooves of the transmission wheels, and of the transmission belt or chain.

[0008] The present invention aims in particular to provide a technically simple solution making it possible to overcome these drawbacks. [Statement of the invention]

[0009] This aim, as well as other advantages which will result from the description which follows, is achieved with a transmission wheel, comprising an outer crown capable of engaging with a transmission belt or chain, and an inner crown, capable of cooperating with a motor member or with a driving wheel, the outer crown comprising a plurality of inner teeth and the inner crown comprising a plurality of outer teeth, remarkable in that the inner and outer teeth are separated by a space filled with an elastomeric material fixed to the outer and inner crowns.

[0010] According to other characteristics of the present invention, taken alone or in combination:

[0011] - the volume defined by the elastomer material has a geometry allowing a reactive transmission of torque between the two crowns, while allowing an angular displacement of the axis of rotation of the outer crown relative to the axis of rotation of the inner crown. By "reactive transmission" is meant a direct and immediate transmission, that is to say ensuring a simultaneous rotation of the crowns as if they formed a single solid unit. This results in a transmission wheel having a dual function: integral transmission of the engine torque and compensation for misalignment with the other transmission wheel;

[0012] - said elastomer material is solid in the areas of mutual drive of the teeth of the outer and inner crowns, and openwork in the areas of absence of mutual drive: this configuration makes it possible to obtain on the one hand a rigidity of the elastomer material between the areas of drive of the teeth, favorable to the integral transmission of the engine torque, and on the other hand a flexibility of this elastomer material in the areas of absence of mutual drive, favorable to the angular movement of the outer crown relative to the inner crown;

[0013] - the surfaces of cooperation of the outer and inner crowns with the elastomer material are spherical: this particular geometry corresponds to the kinematics of angular displacement of the outer crown relative to the inner crown, and makes it possible to distribute in a homogeneous manner the forces applied by the two crowns to the elastomer material;

[0014] - the outer crown includes notches capable of cooperating with a transmission belt: this configuration is particularly suitable for city bikes, classic or electrically assisted, in which the gear changing system is generally housed inside the hub of the driven transmission wheel, and allows a limited number of different speeds;

[0015] - anti-derailment flanges are arranged alternately between the notches of the outer ring: these flanges, in combination with the possibility of angular movement of the outer ring, make it possible to limit the risk of the transmission belt or chain escaping from the transmission wheel;

[0016] - the outer crown and the inner crown are formed from materials, taken alone or in combination, chosen from the group comprising metals such as aluminum, metal alloys, and plastics: the use of these materials makes it possible to obtain a good weight / robustness compromise for the transmission wheel.

[0017] The present invention also relates to a transmission assembly, remarkable in that it comprises a driving transmission wheel and a driven transmission wheel in accordance with the above, and a belt or a chain connecting these two wheels: the presence of two transmission wheels according to the invention in such an assembly makes it possible to optimize the function of compensating for misalignment of one wheel relative to the other.

[0018] The present invention also relates to a vehicle chosen from the group comprising conventional bicycles, electrically assisted bicycles, cargo bicycles, motorcycles, remarkable in that it comprises a transmission assembly in accordance with the above: such a vehicle will require less maintenance due to the lesser wear of the outer teeth of the transmission wheel, and of the transmission belt or chain; it will also have better engine efficiency, due to the reduction in mechanical friction of the belt or chain on the transmission wheels. [Description of the drawings]

[0019] Other characteristics and advantages of the present invention will appear in the light of the description which follows, and on examination of the attached drawings, in which:

[0020] Figure 1 shows, in perspective view from the rear of a bicycle, a transmission belt arranged on two correctly aligned transmission wheels of the prior art,

[0021] Figure 2 shows, in perspective view from the rear of a bicycle, two transmission wheels of the prior art having a parallel misalignment, the transmission belt having been removed,

[0022] Figure 3 shows, in top view, two toothed transmission wheels of the prior art having a parallel misalignment,

[0023] Figure 4 shows, in top view, two prior art grooved transmission wheels exhibiting angular misalignment,

[0024] Figure 5 represents, in perspective, a transmission wheel according to the invention,

[0025] Figure 6 represents, in partially cut-away perspective, the transmission wheel of Figure 5,

[0026] Figure 7 shows a side view of part of the transmission wheel of Figures 5 and 6,

[0027] Figure 8 represents an axial sectional view of the transmission wheel of Figures 5 to 7, taken along line VI I l-VI 11 of Figure 7,

[0028] Figure 9 represents an axial sectional view of the outer toothed crown of the transmission wheel of Figures 5 to 8, cooperating with a transmission belt,

[0029] Figure 10 is a view similar to that of Figure 8, allowing the transmission wheel to be visualized when the outer ring of this wheel is angularly offset relative to the inner ring. [Description of embodiments]

[0030] We now refer to Figure 1, in which we can see a rear wheel 1 of a bicycle mounted on a frame 3, this rear wheel 1 being provided with a driven toothed transmission wheel 5, which can be rotated by a driving transmission wheel 7 via a toothed belt 9.

[0031] In the configuration visible in Figure 1, the driving 7 and driven 5 transmission wheels are correctly aligned, that is to say that the notches of these wheels 5, 7 and the toothed belt 9 are all located substantially in the same plane.

[0032] In the configuration visible in Figure 2, the driving 7 and driven 5 transmission wheels have a parallel misalignment with respect to each other, that is to say they are offset with respect to each other in translation according to the direction of their axes of rotation.

[0033] This parallel misalignment is also shown schematically in Figure 3.

[0034] The arrow F visible in Figure 2 schematically indicates the trajectory of the toothed belt 9 intended to cooperate with the two toothed transmission wheels 5, 7.

[0035] As can be seen, this arrow F has a bend 11, symbolizing the angular offset of the plane of the toothed belt 9 relative to the planes of the respective notches 13, 15 of each of the transmission wheels 5, 7.

[0036] In this configuration of parallel offset of the two transmission wheels 5, 7, the toothed belt 9 does not work optimally because it is then subjected to increased friction in the areas of cooperation with the notches 13, 15 of the two transmission wheels 5, 7.

[0037] Furthermore, there is a significant risk that the toothed belt 9, which runs obliquely to the planes of the two transmission wheels 5, 7, could escape from these wheels, leading to a derailment situation.

[0038] Another configuration in which this risk exists is that visible in Figure 4, on which we can see two transmission wheels 5, 7 - grooved pulleys in this case - which have an angular misalignment: the axes of rotation A1, A2 of each of these wheels 5, 7 are inclined relative to each other, instead of being parallel.

[0039] In this configuration also, the transmission belt 9 connecting the two pulleys 5, 7 risks wearing prematurely and coming out of the grooves of the two pulleys.

[0040] In addition to the aforementioned disadvantages, the misalignment configuration of the transmission wheels 5, 7 can generate noise and lead to a loss of efficiency of the driving energy transmitted by the driving transmission wheel 7 to the driven transmission wheel 5.

[0041] Figures 5 to 9 show a transmission wheel 7 according to the invention making it possible to overcome the aforementioned drawbacks.

[0042] As can be seen in Figures 5 to 7, this transmission route comprises an outer ring 17 provided on its radially outer periphery with a plurality of notches 15 distributed regularly, capable of cooperating with a toothed belt.

[0043] Preferably, these notches 15 are closed laterally by anti-derailment flanges 19, arranged alternately from one notch 15 to the other.

[0044] On its radially inner part, the outer crown 17 is provided with a plurality of internal teeth 21 distributed regularly.

[0045] This outer crown 17, equipped with its notches 15, its flanges 19 and its internal teeth 21, perhaps formed from a single block, by machining or molding a metallic material such as aluminum or a plastic material.

[0046] The transmission wheel 7 according to the invention further comprises an inner crown 23, provided at its radially outer periphery with a plurality of outer teeth 24.

[0047] This inner ring 23 can be formed from the same material as the outer ring 17, or else be formed in two parts as can be seen in FIG. 6, namely a radially inner annular metal part 25, onto which a radially outer plastic part 27 can be overmolded.

[0048] As can be seen more particularly in Figures 6 to 8, the space between the outer and inner crowns is filled with an elastomeric material 29.

[0049] More precisely, as can be seen in particular in FIG. 7, this material 29 fills the space located between the inner teeth 21 of the outer crown 17, and the outer teeth 24 of the inner crown 23.

[0050] The arrow F2 visible in figure 7 represents the rotational torque which is imparted to the transmission wheel 7, which in this case is a driving wheel.

[0051] This torque can be produced by a motor, particularly an electric motor, or by the force of a cyclist.

[0052] As can be seen in Figure 7, in the space of mutual drive of an inner tooth 21a of the outer ring 17 by an outer tooth 24a of the inner ring 23, that is to say in the space of transmission of the driving torque from the inner ring 23 to the outer ring 17 where the elastomeric material 29 works in compression, this elastomeric material 29 is full.

[0053] On the contrary, in the previous space located between the same external tooth 24a of the internal crown 23, and the previous internal tooth 21b of the external crown 17, where the elastomer material 29 does not work in compression, this elastomer material 29 has at least one opening 30, that is to say a zone without material.

[0054] The elastomer material 29 may be synthetic rubber typically having a hardness of the order of 65 shore A.

[0055] This elastomeric material 29 can be connected to the radially inner circumferential walls 31 of the outer ring 17 and radially outer circumferential walls 33 of the inner ring 23 using a particular adhesive product, ensuring a robust and durable of this material with the two crowns 17, 23.

[0056] Referring now to Figure 8, it can be seen that, preferably, the circumferential walls 31, 33 of the outer 17 and inner 23 rings cooperating with the elastomeric material 29, preferably have a spherical axial section (relative to the axis of rotation of the transmission wheel), allowing a ball joint or cardan type connection between the two rings. Indeed, as illustrated by Figure 8, the circumferential walls 31, 33 of the outer 17 and inner 23 rings preferably have, in any section plane passing through the axis of rotation of the transmission wheel, sections which are inscribed in respective concentric circles C1 and C2 whose center corresponds to the intersection of the axis of rotation of the transmission wheel with the plane of the transmission wheel.The radii of the circles C1 and C2 vary from one section plane passing through the axis of rotation to another section plane passing through the axis of rotation, depending in particular on the presence or absence of internal teeth 21 and / or external teeth 24. Figure 8 shows, in the section plane, the circumferential walls 31, 33 of the external 17 and internal 23 crowns on one side of the axis of rotation of the transmission wheel. The same principle also applies, in the same section plane, on the other side of the axis of rotation of the transmission wheel, with concentric circles which may have radii different from the circles C1 and C2 shown in Figure 8, depending in particular on the presence or absence of internal teeth 21 and / or external teeth 24.

[0057] Referring to Figure 9, it can be seen that the anti-derailment flanges 19 arranged between the notches 15 of the transmission wheel 7 have a radial dimension allowing their free edges 35 to cooperate with the inclined parts 37a, 37b of the trapezoidal section of a toothed belt 9 - these inclined parts 37a, 37b can typically have an angle of the order of 65° relative to each other.

[0058] The mode of operation and the advantages of the transmission wheel 7 which has just been described result from the above.

[0059] This transmission wheel 7 can be a driving wheel, in which case the engine torque is received by the inner ring gear 23 (and is transmitted to the outer ring gear 17 by the elastomer material 29), or a driven wheel, in which case the engine torque is received by the outer ring gear 17 (and is transmitted to the inner ring gear 23 by the elastomer material 29).

[0060] In the case of a conventional or electrically assisted bicycle, the driving wheel 7 can be driven by the cyclist's feet, and the driven wheel is fixed to the rear wheel of the bike.

[0061] The notches 13 arranged on the outer periphery of each transmission wheel 5, 7 are intended to cooperate with a toothed belt 9 connecting the two transmission wheels 5, 7 together.

[0062] In the event of parallel or angular misalignment of one transmission wheel relative to the other, the outer ring 17 of each transmission wheel can become angularly misaligned by an angle a as shown in Figure 10 relative to its associated inner ring 23, this being due to the presence of the elastomeric material 29 which allows angular movement of the outer ring 17 relative to the inner ring 23.

[0063] This inclination of each transmission wheel 5, 7 relative to its axis of rotation, which takes place when the toothed belt 9 is tensioned under the driving effect of the driving wheel 7, makes it possible to replace the belt 9 and the two transmission wheels 5, 7 in the same plane.

[0064] This angular movement is facilitated by the openings 30 formed in the elastomer material 29, providing it with a certain flexibility favorable to the movements of the outer crown 17 in a direction parallel to the axis of rotation of the transmission wheel 7.

[0065] The solid part of the elastomer material 29, located in the mutual drive zones of the teeth 21, 24 of the outer 17 and inner 23 crowns, working in compression, offers sufficient rigidity to allow full transmission of the forces between these teeth 21, 24, so that the outer 17 and inner 23 crowns operate in rotation as a single block.

[0066] In other words, the elastomer material 29 fulfills on the one hand the function of angular offset of the outer ring 17 relative to the inner ring 23, and on the other hand of integral transmission of the engine torque between these two rings 17, 23.

[0067] These two functions can thus be obtained in a simple and economical manner, by simple injection then vulcanization of the elastomer material 29 in the space separating the two crowns 17, 23.

[0068] The geometry of this space, as well as the shape and location of the openings 30 formed in the elastomer material 29, can be optimized using computer-assisted sizing tools available to those skilled in the art, so as to achieve the required flexibility of movements of the outer ring 17 relative to the inner ring 23.

[0069] It will be noted that the spherical section of the radially inner walls 31 of the outer ring 17 and the radially outer walls 33 of the inner ring 23 corresponds to the profile of the stroke of the outer ring 17 relative to the inner ring 23, and thus makes it possible to optimize the distribution of forces in the elastomer material 29.

[0070] The presence of the flanges 19 arranged alternately between the notches 15 of the outer ring 17, and cooperating with the inclined parts 37a, 37b of the toothed belt 9, make it possible to limit the risk of this toothed belt 9 coming out of these notches 15 in the event of misalignment of the transmission wheels.

[0071] As will be understood in light of the above, the present invention provides a simple and inexpensive solution for solving the problem of parallel and / or axial misalignment of the transmission wheels 5, 7 with respect to each other.

[0072] The teachings of the present invention could also be applied to transmission wheels of the grooved pulley type cooperating with a smooth belt, or to transmission wheels of the sprocket type cooperating with a chain.

[0073] An assembly comprising two transmission wheels according to the invention connected to each other by a belt or a chain are particularly suitable for a classic or electrically assisted bicycle or cargo bike.

[0074] It should be noted, however, that such a set could have other applications, and be installed, for example, on a motorcycle, or in a motor vehicle, or even in industry.

Claims

Claims

1. Transmission wheel (5, 7), comprising an outer crown (17) capable of engaging with a belt (9) or transmission chain, and an inner crown (23), capable of cooperating with a driving member or with a driving wheel, the outer crown (17) comprising a plurality of inner teeth (21) and the inner crown (23) comprising a plurality of outer teeth (24), characterized in that the inner (21) and outer (24) teeth are separated by a space filled with an elastomeric material (29) fixed to the outer (17) and inner (23) crowns, and in that the surfaces of cooperation of the outer (17) and inner (23) crowns with the elastomeric material (29) are spherical.

2. Transmission wheel (5, 7) according to claim 1, characterized in that the volume defined by the elastomeric material (29) has a geometry allowing a reactive transmission of torque between the two crowns (17, 23), while allowing an angular movement of the axis of rotation of the outer crown (17) relative to the axis of rotation of the inner crown (23).

3. Transmission wheel (5, 7) according to claim 2, characterized in that said elastomeric material (29) is solid in the areas of mutual drive of the teeth (21, 24) of the outer (17) and inner (23) crowns, and perforated (30) in the areas of absence of mutual drive.

4. Transmission wheel (5, 7) according to any one of the preceding claims, characterized in that the outer crown (17) comprises notches (13, 15) capable of cooperating with a transmission belt (9).

5. Transmission wheel (5, 7) according to claim 4, characterized in that anti-derailment flanges (19) are arranged alternately between the notches (13, 15) of the outer crown (17).

6. Transmission wheel (5, 7) according to any one of the preceding claims, characterized in that the outer ring (17) and the inner ring (23) are formed from materials, taken alone or in combination, chosen from the group comprising metals such as aluminum, metal alloys, and plastics.

7. A transmission assembly, characterized in that it comprises a driving transmission wheel (7) and a driven transmission wheel (5) according to any one of the preceding claims, and a belt (9) or a chain connecting these two wheels (5, 7).

8. Vehicle chosen from the group comprising bicycles and motorcycles, characterized in that it comprises a transmission assembly according to claim 7.

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