Selection system for an improved gearshift for a bicycle

Abstract

A selection system (8) for selecting one of a plurality of gear wheels (4', 4'') forming part of a shifting system (1) for a bicycle and carried in a free rotational manner by a shaft (5) of a transmission of the shifting system (1) and rotating around an axis (A), the selection system (8) comprising a screw-nut system configured to assume a first configuration in which it makes one of the gear wheels (4', 4'') integral with the shaft (5) or a second configuration in which it makes another of the gear wheels (4', 4'') integral with the shaft (5), and actuator means (9) configured to control an element of the screw-nut system to bring it from the first to the second configuration.

Description

[0001] "SELECTION SYSTEM FOR AN IMPROVED GEARSHIFT FOR A BICYCLE"

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This Patent Application claims priority from Italian Patent Application No . 102023000015609 filed on July 25 , 2023 , the entire disclosure of which is incorporated herein by reference .

[0004] TECHNICAL FIELD

[0005] The present invention relates to a selection system for a gearshi ft , in particular a shi fting system for bicycles .

[0006] The present invention finds its preferred, though not exclusive , application in a hybrid type gearshi ft for bicycles . This application will be referred to hereinafter by way of example .

[0007] STATE OF THE PRIOR ART

[0008] Pedal vehicles , such as a bicycle , are increasingly being used as a movement system both for leisure purposes and for reasons of necessity, such as the transport of goods , especially in cities .

[0009] In order to ensure that increasingly longer routes or steeply inclined routes are covered, hybrid drive systems for bicycles are well known .

[0010] In purely mechanical or hybrid drive systems , it is necessary to provide a transmission with shi fting systems which, as is known, allow the selection of di f ferent gear wheels forming part of di f ferent gear trains in order to vary the gear ratio between the input and the output of the transmission .

[0011] In particular, the aforementioned wheels are normally carried idly by the respective support shaft and can be selectively fixed thereto by selection systems .

[0012] However, these selection systems are inaccurate and bulky .

[0013] There is therefore a need to solve the technical issues with regard to the systems of the prior art as reported above .

[0014] The obj ect of the present invention is to meet the above need in an optimi zed and cost-ef fective manner .

[0015] SUMMARY OF THE INVENTION

[0016] Said obj ect is achieved by means of a selection system for a gearshi ft , a shifting system, and a bicycle , as claimed in the appended claims .

[0017] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a better understanding of the present invention, a preferred embodiment is described below by way of nonlimiting example and with reference to the accompanying drawings , wherein :

[0019] • Figure 1 is a perspective view of a portion of a shi fting system for a bicycle according to the invention, with parts removed for clarity; • Figure 2 is a longitudinal sectional view of the portion of a shifting system shown in Figure 1 in a first operating condition;

[0020] • Figure 3 is a cross-sectional view of the portion of a shifting system shown in Figure 1; and

[0021] • Figure 4 is a longitudinal sectional view of the portion of a shifting system shown in Figure 1 in a second operating condition.

[0022] DETAILED DESCRIPTION OF THE INVENTION

[0023] In the attached figures, 1 indicates a portion of a shifting system 1 forming part of a transmission (not shown) for a bicycle (not shown) .

[0024] The shifting system 1 is housed within a space 3 defined by a casing 2. The casing 2 comprises at least a first wall 2' configured to support a rotating shaft 5 of the transmission extending along its longitudinal axis A and rotationally supporting a plurality of gear wheels 4' , 4' ’ . The exemplary embodiment shows two gear wheels 4', 4' ' but it is clear that there can be as many as necessary for the need for gear ratios that can be defined by the shifting system 1.

[0025] The gear wheels 4', 4' ' are part of respective gears or gear trains of the aforementioned transmission, and the shifting system 1, as is known, is configured to define respective gear ratios according to the selection of one (or more) of the aforementioned gear wheels 4', 4' ' depending on the selected gear ratio.

[0026] In particular, the rotating shaft 5 is supported in relation to the casing 2 by support elements 6 such as rolling bearings. Advantageously, the rotating shaft 5 is hollow and therefore defines a cylindrical space 7 therein along the axis A.

[0027] The shifting system 1 comprises a selection system 8 configured to assume a first configuration in which it selects a first gear wheel 4' of said plurality of gear wheels 4' , 4' ', making it integral with the rotating shaft 5, and a second configuration in which it selects a second gear wheel 4' ' of said plurality of gear wheels 4' , 4' ', making it integral with the rotating shaft 5.

[0028] In particular, the shifting system 1 comprises actuator means 9 configured to shift the selection system 8 from the above-mentioned first to the above-mentioned second configuration .

[0029] Advantageously, at least the selection system 8 is entirely housed in the space 7. The actuator means 9 can be housed in the space 7 or, as in the described embodiment, be housed in a seat 2' ' obtained in the wall 2' .

[0030] In detail, the selection system 8 comprises a screw-nut system configured to selectively cooperate with one or the other of the gear wheels 4' , 4' ’ , making them integral with the rotating shaft 5 . Advantageously, the selection system

[0031] 8 comprises a screw 11 and a nut , also referred to in the following as a " slide" 12 .

[0032] The screw 11 extends along the axis A, advantageously coaxial therewith, and comprises an actuation portion 11 ' ' configured to be operatively connected to the actuator means

[0033] 9 to drive the screw 11 into rotation around the axis A, and a main portion 11 ' ' defining a thread appointed for this purpose .

[0034] The slide 12 is tubular in shape and is carried by the screw 11 in order to translate along the axis A. Advantageously, therefore , the slide 12 comprises an actuator portion 12" defining on its internal tubular surface a thread suitable to cooperate with the thread of the main portion 11 ' ' .

[0035] The slide 12 further comprises a cooperation portion 12 ' cooperating with a spacer 13 rigidly carried by the casing 2 .

[0036] In particular, the spacer 13 is fitted inside the casing 2 , in contact therewith and fixed thereto by interference or, for example , by means of a key, in an opening 14 made in the casing 2 .

[0037] In detail , the cooperation between the slide 12 and the spacer 13 is such that the rotation of the slide 12 around the axis A is inhibited, however, its linear movement along this direction is permitted .

[0038] In particular, support means between the slide 12 and the spacer 13 may be provided to facilitate their mutual sliding, such as a bushing made of low- friction material such as Teflon .

[0039] The actuator portion 12" defines an annular seat 16 made on the outer tubular surface thereof and configured to house a plurality of rolling elements 17 such as , for example , a plurality of balls . In the described embodiment there are three rolling elements , such as balls , angularly equally spaced circumferentially around the axis A, as best visible in Figure 3 .

[0040] The elements 17 are dimensioned to have a diameter such that they radially protrude from the annular seat 16 , which defines a curvature suitable to allow the roto-translation of the elements 17 , namely a rotation around the axis A and a translation along the axis A. Accordingly, the rotating shaft 5 defines a plurality of slots 5 ' located radially in relation to the annular seat 16 , the number of which is equal to the number of rolling bodies 17 .

[0041] Advantageously, although not clearly visible in the attached schematic exemplary drawings , the slots 5 ' are shaped like a spiral around the axis A in order to follow the roto-translatory movement of the elements 17 .

[0042] These numerous slots 5 ' are each dimensioned, radially in relation to the axis A, to allow the passage of the rolling elements 17, circumferentially in relation to the axis A, to allow a minimum clearance suitable for allowing the rotation of the rolling elements 17 along the seat 16, and roto-translationally in relation to the axis A, as a function of the travel and rotation of the slide 12 along the screw 11.

[0043] Each gear wheel 4', 4' ' is configured, as mentioned, to be fitted via a respective hub onto the shaft 5, and in particular around the slots 5' . Each gear wheel 4', 4' ' defines a plurality of housings 18 for the rolling elements 17, preferably circumferentially equally spaced along the axis A.

[0044] As best visible in Figure 3, the housings 18 are created through a succession of recesses 18' ' interspersed with partition walls 18' ' . In other words, the plurality of recesses 18' ' is created on the internal tubular surface of the hub of the gear wheels 4', 4' ' , thus defining a toothed type profile given by the partition walls 18' .

[0045] The recesses 18' ' are each dimensioned, radially in relation to the axis A, to allow the housing of the rolling elements 17, and circumferentially in relation to the axis A, to allow a minimum clearance suitable for allowing the roto-translation of the rolling elements 17 along the same recesses 18' ' . The actuator means 9 advantageously comprise a gear train and, better still, an epicyclic / planetary mechanism which can be operated, for example, by an electric machine, not shown, carried by the wall 2' of the casing 2, or by a mechanical drive such as a cable mechanism or other known types of actuation, according to the user's manual shift request or a shift request through a mechanical, electrical and / or fluidic signal.

[0046] In detail, the wall 2' defines an opening 2' ' configured to house the above planetary mechanism, and preferably the opening 2' ' faces, axially in relation to the axis A, the opening 14 housing the spacer 13.

[0047] Preferably, the planetary gear train comprises a sun wheel 9', a plurality of satellites 9' ' meshing around the sun wheel 9', and a crown 9' ’ ’ containing the sun wheel 9' and the satellites 9’' and meshing with the latter.

[0048] Advantageously, the satellites 9' ' can be driven by the above actuation into rotation around the sun wheel 9', causing it to rotate with a high transmission ratio.

[0049] Preferably, the sun wheel 9' is rigidly fitted on the actuation portion 11' of the screw 11 so that, when moved by the satellites 9*' , it drives the screw 11 into rotation around the axis A. As a result, a rotation in one or the other direction of rotation around the axis A can make the screw 11 move in that direction of rotation, and consequently the slide 12 can move in one direction or the other along the axis A.

[0050] The operation of the above-described embodiment of the bicycle gearshift selection system according to the invention is as follows.

[0051] In a first operative configuration (Figure 2) , the rolling elements 17 cooperate in contact in the housings 18 made in the first gear wheel 4' , thus creating an integral coupling between the first gear wheel 4' and the hollow shaft 5. Therefore, the first gear wheel 4' can be driven into rotation by a respective counterpart (not shown) , thus driving the shaft 5, or be driven by the shaft 5, thus rotating its counterpart, depending on the composition of the bicycle transmission. In this configuration, the second gear wheel 4' ' is carried idly on the shaft 5.

[0052] If it is desired to shift between the first and the second gear wheel 4' , 4' ’ , the actuator means 9 are controlled to drive into rotation the screw 11, which moves the slide along the axis A, moving away from the spacer 13. As it moves away, the rolling elements 17 tend to exit the housing 18 of the first gear wheel 4' and enter the housing 18 of the second gear wheel 4' ', thus making the second gear wheel integral with the shaft 5 and making the first gear wheel idle (Figure 4) .

[0053] If it is desired to shift again by returning to the first gear wheel 4', it will be sufficient to reversely actuate the actuator means 9 which will vary the position of the slide 12 in relation to the spacer 13 (bringing them closer to each other) , returning to the configuration shown in Figure 2.

[0054] The advantages of a bicycle gearshift selection system according to the invention are clear from the foregoing.

[0055] The proposed gearshift selection system allows a very precise and compact shifting system to be provided.

[0056] In fact, the shifting system is substantially housed within the shaft supporting the same gear wheels, and the use of a screw-nut system allows the passage between one or the other gear wheel to be finely adjusted.

[0057] In detail, the actuation via a planetary gear train is also extremely compact and effective.

[0058] Furthermore, it is possible to size the elements of the shifting system for different types of use of the bicycle, and therefore of gear wheels used.

[0059] Lastly, it is clear that modifications and variations may be made to the bicycle gearshift selection system according to the present invention, without however departing from the scope of protection defined by the claims.

[0060] As mentioned, there may be more gear wheels, more or fewer rotating elements than those illustrated. Clearly, the geometry of the casing 2 may vary and the transmission may comprise more shafts provided with a shifting system of the aforementioned type.

[0061] Furthermore, the described screw-nut system or gear train can be made differently.

Claims

CLAIMS1.- A selection system (8) for selecting a gear wheel (4', 4' ' ) among a plurality of gear wheels (4', 4' ' ) forming part of a shifting system (1) for a bicycle and carried in a free rotational manner by a shaft (5) of a transmission of said shifting system (1) rotating around an axis (A) , said selection system (8) comprising a screw-nut system configured to assume a first configuration in which it makes one of said gear wheels (4', 4' ' ) integral with said shaft (5) or a second configuration in which it makes another of said gear wheels (4', 4' ' ) integral with said shaft (5) , and actuator means (9) configured to control an element of said screw-nut system to bring it from said first to said second configuration, wherein said screw-nut system comprises a screw (11) and a slide / nut (12) , said actuator means (9) rotating said screw (11) around said axis (A) , said slide (12) being coupled via a threaded coupling to said screw (11) so as to move linearly along said axis (A) according to the rotation of said screw (11) , wherein said screw-nut system comprises a spacer (13) rigidly carried by said casing (2) and configured to prevent the rotation of said slide (12) around said axis (A) allowing only its longitudinal movement along said axis (A) ,wherein said slide (12) comprises a cooperation portion (12' ' ) cooperating with said spacer (13) and an actuator portion (12' ) cooperating through said threaded connection with said screw (11) , said actuator portion (12' ) defining an annular seat (16) able to house one or more rolling elements (17) configured to cooperate selectively in housings (18) obtained in said gear wheels (4', 4' ' ) , according to the axial movement of said slide along said axis (A) .2.- The selection system according to claim 1, wherein said screw (11) comprises a main portion (11' ' ) cooperating with said slide (12) and an actuation portion (11' ) operatively connected to said actuator means (9) .3.- The selection system according to claim 1 or 2, comprising a plurality of rolling elements (17) angularly spaced equally around said axis (A) .4.- The selection system according to one of the preceding claims, wherein said housings (18) are made as radial recesses (18' ' ) in said hub of said gear wheels (4', 4 ' ' ) .5.- The selection system according to one of the preceding claims, wherein said shaft (5) respectively defines one or more slots (5' ) configured to allow the passage of said one or more rolling elements (17) between said seat (16) and said gear wheels (4', 4' ' ) .6.- The selection system according to claim 5, wherein said slots (5' ) have a spiral shape around said axis (A) .7.- The selection system according to one of the preceding claims, wherein said actuator means (9) comprise an epicyclic / planetary gear train.8.- The selection system according to claim 7, wherein said actuator means comprise a sun wheel (9' ) rigidly carried by said screw (11) , a crown (9' ' ' ) rigid to rotation, and a plurality of satellites (9' ' ) driven into rotation according to a request to pass from said one to said other of said gear wheels (4 ' , 4 ' ' ) .9.- A shifting system (1) for a transmission of a bicycle, said shifting system (1) comprising at least one shaft (5) rotating with respect to a casing (2) and at least one pair of wheels (4', 4' ' ) configured, when integral with the rotation of said shaft (5) , to define a transmission ratio of said shifting system (1) , said shifting system (1) comprising a selection system (8) according to any one of the preceding claims.10.- The shifting system according to claim 7, wherein said casing (2) comprises a wall (2' ) defining an opening (14) housing said spacer (13) .11.- The shifting system according to claim 9 or 10, wherein said casing (2) comprises a wall (2' ) defining an opening (2' ' ) housing said actuator means (9) .12.- The shifting system according to claims 10 and 11, wherein said openings (14, 2' ' ) face each other axially.13.- A bicycle comprising a shifting system according to one of claims 9 to 12.

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