Instrument-equipped bicycle component and detection unit for equipping such a component

0001The present invention relates to an instrument-equipped bicycle component. In particular, the invention relates to an instrument-equipped bicycle component for detecting the stresses imparted upon the component.

0002The invention also relates to a detection unit used to equip the aforementioned bicycle component and a bicycle comprising the aforementioned component.

0003In cycling, above all at the professional level, there are many reasons why it is advantageous to detect parameters that are representative of the stresses imparted upon a bicycle component.

0004For example, the detection of the aforementioned parameters provides useful information in order to design the component. Indeed, a constant requirement for manufacturers of bicycles and/or of bicycle components, above all racing bicycles, is to reduce as much as possible the overall weight of the bicycle and, therefore, of the various components thereof, at the same time maintaining, if not even improving, the characteristics of structural strength of such components. In order to do this it is necessary to know the extent of the stresses to which the components are subjected. For example, in the case of rotating components of the bicycle, like the shaft of the bottom bracket assembly, the crank arm or a component of the bicycle wheel, the torsional deformation of such components can be measured in order to know the extent of the aforementioned stresses.

0005The detection of the parameters representative of the stresses imparted by the cyclist upon a bicycle component while pedalling also allows the performance of the cyclist to be evaluated and possibly compared. For example, the measurement of the torsional deformation of a rotating component of the bicycle makes it possible to know the power developed by the cyclist while pedalling and, therefore, to evaluate his performance.

0006<patcit id="pcit0001" dnum="US6701793B"><text>US 6,701,793</text></patcit> discloses a sensor for measuring the torque applied to a shaft. Such a sensor comprises a layer of magnetostrictive material applied to the shaft, a first electrical winding wound around the shaft at the layer of magnetostrictive material, a second electrical winding wound around the shaft inside the first winding and a signal generator adapted to supply a current signal to the first electrical winding so as to generate a magnetic field. When a torque is applied to the shaft, the permeability of the magnetostrictive material varies, causing a variation in magnetic flux about the shaft. Due to such a variation on the second electrical winding a tension signal is generated that is measured and used to determine the magnitude and direction of the applied torque.

0007The Applicant observes that the sensor described above requires particularly laborious operations to be installed in a bicycle component. For example, in the case of a bottom bracket assembly, both a specific adaptation of the box housing the bottom bracket assembly to receive the electrical windings and a preparation of the surface of the shaft for the application of the layer of magnetostrictive material is required. It is thus necessary to intervene on many elements, and in particular both on an element that while pedalling remains fixed with respect to the bicycle frame (in the example described above, the box housing the bottom bracket assembly) and on an element that while pedalling moves with respect to the bicycle frame (the shaft of the bottom bracket assembly). The fact that the sensor is associated both with a fixed element and with a mobile element implies an air transmission of the signal generated in the sensor. The detection of such a signal can thus be distorted by possible misalignments or shielding between the various elements.

0008The technical problem at the basis of the present invention is that of allowing the measurement of the stress imparted by the cyclist upon a bicycle component while pedalling through a simple, cost-effective, reliable and easy-to-install system.

0009The invention therefore relates, in a first aspect thereof, to an instrument-equipped bicycle component, such a component comprising a detection unit of at least one parameter representative of a stress imparted upon the component, the component being a single piece or comprising more parts that do not move relative to one another.

0010Throughout the present description and in the following claims, the "component" to which we refer is either any component of the bicycle that, while the bicycle is travelling, remains fixed with respect to the bicycle frame, like for example the frame itself (or a part thereof), or the seat post, or any component that while the bicycle is travelling moves with respect to the frame, like for example the shaft of the bottom bracket assembly or the crank arm. Moreover, the component of the present invention can be formed in a single piece (like for example the crank arm) or in many pieces (like for example the bottom bracket assembly). In accordance with the present invention, in the latter case the detection unit is associated with one of these pieces or with more pieces, such pieces, however, not moving relative to one another or moving as a single piece.

0011Advantageously, in accordance with the present invention the entire detection unit is associated with parts of the component of the bicycle that do not move with respect to one another. In the step of manufacturing the instrument-equipped component and of assembly of such a component on the bicycle, there is therefore only intervention on parts of the component that are intended to remain fixed with respect to the bicycle frame while the bicycle is travelling or that move as a single piece with respect to the frame, with clear advantages in terms of cost and manufacturing and assembly time. Moreover, since no interaction is needed between fixed elements and mobile elements, the detection of the parameter representative of the stress imparted by the cyclist upon the component while pedalling is particularly simple, reliable and effective.

0012Preferably, the component of the present invention is a rotating component. It comprises, in particular, a main body that can rotate about a rotation axis. In this case, the aforementioned detection unit rotates as a single piece with the aforementioned main body.

0013Preferably, the detection unit comprises at least one generator of at least one signal (preferably an electrical signal) representative of the stress imparted upon the component and, more preferably, at least one transmission device of this signal outside of the detection unit. The detection unit also preferably comprises at least one power supply source (preferably an electrical energy source) and, even more preferably, at least one processing unit of the signal generated by the signal generator.

0014The power supply source can, for example, be a battery, a piezoelectric element (in particular a crystal) or an induction winding excited by a fixed magnet arranged close to the rotating component. The signal generator can consist of one or more strain-gauges or a piezoelectric element (possibly the same one that constitutes the power supply source). The transmission device of the signal can consist of a radio transmitter or can comprise cables with sliding contacts or solenoids.

0015In the case in which a battery is used as power supply source, the signal generator acts upon a constant electrical signal emitted by the battery to generate a signal representative of the stress imparted upon the component. On the other hand, in the case in which a piezoelectric element is used, since the piezoelectric element by its very nature autonomously generates an electrical signal directly proportional to the magnitude of the stress to which it is subjected, it acts both as a power supply source and as a signal generator. In this case the piezoelectric element is made so as to be compressed by the stress imparted by the cyclist upon the component while pedalling.

0016In a first embodiment of the component of the present invention, the component is made from composite material and the detection unit is at least in part incorporated in the composite material. Preferably, in this case the signal generator consists of a piezoelectric element incorporated in the body of a crank arm made from carbon fibre.

0017In the preferred embodiment of the component of the present invention, the detection unit is at least in part housed in at least one cavity of the component. Preferably, the elements of the component of the present invention that are housed in the cavity of the component are the power supply source and, more preferably, also the transmission device of the signal.

0018In the preferred embodiment of the component of the present invention, the signal generator is also housed in the aforementioned cavity, so that the entire detection unit is located inside the body of the component of the present invention.

0019Nevertheless, alternative embodiments of the component of the present invention are foreseen in which some of the aforementioned elements are associated with an outer surface of the component. In particular, an alternative embodiment is foreseen in which the signal generator is associated with the outer surface of the component. This can be particularly advantageous in cases in which one wishes to detect the tension generated by a torsional stress. Indeed, such a stress is of a greater magnitude precisely at the outer surface of the component and therefore the arrangement of the signal generator right at such a surface allows the efficiency of the detection to be improved.

0020Preferably, the detected parameter is a signal representative of the tensional state of said component. More preferably, said signal is compared with a reference signal to indicate when critical tensions are reached or to indicate that it is necessary to replace the component.

0021Preferably, the parameter detected by the aforementioned detection unit is a signal representative of the torque imparted upon the component by the cyclist while pedalling.

0022In the preferred embodiments of the present invention, the component that is equipped is the shaft of a bottom bracket assembly, the crank arm of such an assembly, a component of the bottom bracket assembly itself or more preferably a threaded element, such as a nut or a screw, used in the bottom bracket assembly. Nevertheless, alternative embodiments of the present invention can be provided in which bicycle component other than those mentioned above are equipped, like for example components of a wheel (for example the hub or the rim), the seat post, the handlebars or the frame of the bicycle.

0023In the specific case in which the component that is equipped is a bottom bracket assembly, both the power supply source and the transmission device are associated with the shaft of the bottom bracket assembly, whereas the signal generator is associated with each of the crank arms. Advantageously, such an embodiment is particularly advantageous considering the fact that in modern bottom bracket assemblies the shaft is only subjected to torsion when the cyclist acts upon the left crank arm, the right crank arm being directly coupled with the front sprockets on which the chain acts to transmit motion to the rear wheel. In such assemblies, therefore, if the signal generator were associated just with the shaft, a partial detection of the torque applied by the cyclist would be obtained. The positioning of the signal generators on the crank arms, on the other hand, allows this problem of partial detection to be overcome.

0024Preferably, the power supply source and the transmission device are defined by modular elements connected together through electrical connectors.

0025The signal generator and the transmission device, on the other hand, are preferably connected to one another through electrical cables. The use of cables is advantageous compared to connectors by virtue of the fact that the signal to be transmitted is, in general, of little magnitude and would be dispersed if transmitted through connectors.

0026Preferably, the power supply source is an active energy source, i.e. a source capable of producing energy irrespective of the interaction between fixed elements and mobile elements. For example, a battery or a piezoelectrical crystal are active sources.

0027In a preferred embodiment of the component of the present invention, the power supply source is a battery. Such a battery is preferably of the rechargeable type, and even more preferably of the type that is rechargeable by induction, so as to be able to be housed in an area that is airtight and insulated from the outside.

0028Preferably, the signal generator comprises at least one strain-gauge connected to the battery. More preferably, the signal generator comprises two strain-gauges arranged according to perpendicular directions (placed one above the other or arranged in diametrically opposite areas of the shaft), or two pairs of strain-gauges in which the strain-gauges of each pair are arranged according to perpendicular directions, or four strain-gauges connected so as to define a strain-gauge bridge, in particular according to a differential scheme, like a Wheatstone bridge.

0029In an embodiment of the component of the present invention, the transmission device comprises sliding contacts to transmit to the outside the electrical signal generated, representative of the detected parameter.

0030Alternatively, the transmission device comprises a radio frequency transmitter that transmits an electromagnetic signal remotely, for example to a bicycle-computer associated with the handlebars of the bicycle. In this case, preferably, the antenna is housed in at least one cavity of the component open towards the outside, so as not to be shielded by walls of the component.

0031Alternatively, the transmission device comprises a pair of solenoids adapted to generate a magnetic field.

0032Preferably, the detection unit also comprises a power supply device for the transmission device. More preferably, such a power supply device is the same power supply source as for the detection unit, but an alternative embodiment of the component of the present invention is provided in which the power supply device for the transmission device is an additional energy source.

0033Preferably, the detection unit also comprises a signal amplifier arranged between the signal generator and the transmission device and possibly also an analogue/digital converter operatively upstream of said transmission device. In this case, preferably, the detection unit comprises a power supply device for such an amplifier. Preferably, such a power supply device is the same power supply source as for the detection unit, but an alternative embodiment of the component of the present invention is provided in which the power supply device for the amplifier is an additional energy source.

0034Preferably, the detection unit comprises a switch for actuating the power supply source. Advantageously, the use of such a switch allows the power supply source to be deactivated when one does not wish to carry out any detection, so as to minimise energy consumption of the power supply source.

0035Preferably, the aforementioned switch comprises a movement sensor that, advantageously, activates the detection unit following a movement of the bicycle or of the component on which such a sensor is applied.

0036The detection unit also comprises, preferably, an operation indicator LED.

0037Preferably, the detection unit also comprises a calibration or diagnosis switch, which can be defined by a button, a proximity switch, a reed-type switch, etc..

0038Preferably, the detection unit also comprises a cadence sensor which is capable of detecting the speed of rotation of the component simultaneously to the torque applied to the component, so as to calculate the power developed by the cyclist.

0039In a second aspect thereof, the present invention relates to a detection unit for equipping a bicycle component, characterised in that it is configured so that it can be inserted in at least one cavity of the aforementioned component.

0040Preferably, such a detection unit has, individually or in combination, all of the structural and functional characteristics discussed above with reference to the detection unit of the component of the present invention and therefore has all of the aforementioned advantages.

0041In a third aspect thereof, the invention relates to a bicycle comprising an instrument-equipped component of the type described above.

0042Preferably, such a bicycle has, individually or in combination, all of the structural and functional characteristics discussed above with reference to the component of the present invention and therefore has all of the aforementioned advantages.

0043Further characteristics and advantages of the present invention shall become clearer from the following detailed description of some preferred embodiments thereof, made with reference to the attached drawings. In such drawings: <ul id="ul0001" list-style="dash"><li><figref idref="f0001">figure 1</figref> is a schematic longitudinal sectional view of a first embodiment of a bicycle component, in this specific case a bottom bracket assembly, in accordance with the present invention;</li><li><figref idref="f0002">figures 1a-1c</figref> illustrate block diagrams of alternative embodiments of the detection unit of the component of <figref idref="f0001">figure 1</figref>;</li><li><figref idref="f0003">figure 2</figref> is a schematic longitudinal sectional view of a second embodiment of the bicycle component of the present invention;</li><li><figref idref="f0004">figure 3</figref> is a schematic longitudinal sectional view of a third embodiment of the bicycle component of the present invention;</li><li><figref idref="f0005">figure 4</figref> is a schematic longitudinal sectional view of a fourth embodiment of the bicycle component of the present invention;</li><li><figref idref="f0006">figure 5</figref> is a schematic longitudinal sectional view of a fifth embodiment of the bicycle component of the present invention;</li><li><figref idref="f0007">figure 6</figref> is a schematic longitudinal sectional view of a sixth embodiment of the bicycle component of the present invention;</li><li><figref idref="f0008">figure 7</figref> is a schematic longitudinal sectional view of a seventh embodiment of the bicycle component of the present invention;</li><li><figref idref="f0009">figure 8</figref> is a schematic longitudinal sectional view of an eighth embodiment of a portion of the bicycle component of the present invention;</li><li><figref idref="f0010">figure 9</figref> is a schematic longitudinal sectional view of a ninth embodiment of the bicycle component of the present invention;</li><li><figref idref="f0011">figure 10</figref> is a schematic longitudinal sectional view of a tenth embodiment of the bicycle component of the present invention;</li><li><figref idref="f0012">figure 11</figref> schematically illustrates the tensional state of a shaft of a bottom bracket assembly subjected to a torque;</li><li><figref idref="f0012">figure 12a</figref> schematically illustrates the position of the crank arms of a bottom bracket assembly with respect to the shaft of <figref idref="f0012">figure 11</figref> in a starting-thrust condition;</li><li><figref idref="f0012">figure 12b</figref> schematically illustrates the tensional state of the shaft of <figref idref="f0012">figure 11</figref> in the starting-thrust condition;</li><li><figref idref="f0012">figure 12c</figref> schematically illustrates the position of the crank arms with respect to the shaft of <figref idref="f0012">figure 11</figref> in a maximum thrust condition;</li><li><figref idref="f0013">figure 12d</figref> schematically illustrates the position of the crank arms with respect to the shaft of <figref idref="f0012">figure 11</figref> in an end-thrust condition;</li><li><figref idref="f0013">figure 13</figref> schematically illustrates a preferred position of a strain-gauge on the shaft of <figref idref="f0012">figure 11</figref>;</li><li><figref idref="f0014">figure 14a</figref> schematically illustrates the tensional state of the shaft of <figref idref="f0012">figure 11</figref> when subjected to a bending and torsional stress with the crank arms in a first operative position, and a preferred configuration of positioning of the strain-gauges;</li><li><figref idref="f0014">figure 14b</figref> schematically illustrates the tensional state of the shaft of <figref idref="f0012">figure 11</figref> when subjected to a bending and torsional stress with the crank arms in a second operative position, and a preferred configuration of positioning of the strain-gauges;</li><li><figref idref="f0015">figure 15a</figref> schematically illustrates a further configuration of positioning of two strain-gauges on the shaft of <figref idref="f0012">figure 11</figref>;</li><li><figref idref="f0015">figure 15b</figref> schematically illustrates a particularly preferred configuration of positioning of the strain-gauges on the shaft of <figref idref="f0012">figure 11</figref>;</li><li><figref idref="f0016">figure 16</figref> is a side view of a further embodiment of the component of the present invention;</li><li><figref idref="f0017">figure 17</figref> is an exploded perspective view of a further embodiment of the component of the present invention;</li><li><figref idref="f0018">figure 18</figref> shows an enlarged detail of <figref idref="f0017">figure 17</figref>;</li><li><figref idref="f0019">figure 19</figref> is an exploded perspective view of a further embodiment of the component of the present invention;</li><li><figref idref="f0020">figure 20</figref> is a schematic longitudinal sectional view of a further embodiment of the component of the present invention;</li><li><figref idref="f0021">figure 21</figref> is a side view of a bicycle that incorporates the component of the present invention.</li></ul>

0044Throughout the present description, the invention shall be described with reference to a bottom bracket assembly. Nevertheless, it should be understood that the invention can be applied to any bicycle component, like for example a crank arm, a shaft, a wheel component, the frame, the seat post, the handlebars, or any other part of the bicycle.

0045With reference to the various embodiments described hereafter, the expression "bicycle bottom bracket assembly", is used to indicate the assembly obtained by coupling two crank arms with the opposite ends of a shaft. The shaft can be made in a distinct piece from the crank arms or be made in a single piece with one of the two crank arms. The shaft can also be made in a single piece or be obtained by coupling together two or more shaft elements.

0046In this context, the component of the bottom bracket assembly consisting of a crank arm and a shaft (or shaft element) coupled together or made in a single piece is identified with the expression "crank arm assembly".

0047With reference to <figref idref="f0001">figure 1</figref>, a bottom bracket assembly of a bicycle in accordance with a first embodiment of the present invention is indicated with 1.

0048The assembly 1 comprises two crank arm assemblies 5, 6, each comprising a crank arm 17, 18, solid or hollow, made from metal or composite material, and a hollow shaft element 21, 22. The crank arm 17 constitutes the right crank arm on which the front sprockets (not illustrated) intended to engage with the chain are mounted, whereas the crank arm 18 constitutes the left crank arm of the bottom bracket assembly 1.

0049The two shaft elements 21, 22, when coupled together head-to-head as illustrated in <figref idref="f0001">figure 1</figref>, define the shaft 23 of the bottom bracket assembly 1. Such a shaft 23 extends along a longitudinal axis X.

0050The crank arm assemblies 5, 6 are coupled together at first free end portions 29, 30 of the shaft elements 21, 22. At such end portions 29, 30, the shaft elements 21, 22 comprise respective front toothings 25, 26, preferably identical and of the Hirth type, which allow a precise centring between the crank arm assemblies 5, 6.

0051At the second free end portions 27, 28 of the shaft elements 21, 22 a threading is provided for the coupling with the crank arms 17, 18. The coupling between shaft elements 21, 22 and crank arms 17, 18 can however take place according to different ways, for example through gluing, by interference or through coupling of grooved surfaces.

0052The bottom bracket assembly 1 is housed in a substantially tubular housing box 2 suitably formed in the frame of the bicycle. In the housing box 2 the crank arm assemblies 5, 6, and therefore the shaft 23 defined by the shaft elements 21 and 22, are supported in rotation about the longitudinal axis X through bearings 13, 14 fitted on the shaft elements 21, 22 at the respective end portions 27, 28 for coupling with the crank arms 17, 18. The bearings 13, 14 are operatively arranged between the shaft elements 21, 22 and respective adaptor rings 3, 4 screwed inside the opposite ends of the housing box 2. The bearings 13, 14 are positioned outside the housing box 2, each arranged between an adaptor ring 13, 14 and the respective shaft element 21, 22.

0053Suitable gaskets 3a, 4a associated with the adaptor rings 3, 4 on axially opposite sides ensure the hermetic insulation of the bearings 13, 14 from the external environment. An undulated spring 4b is then arranged between the outer ring of the bearing 14 and the adaptor ring 4.

0054The end portions 29, 30 of the shaft elements 21, 22 respectively have a through hole 31 and a threaded hole 32, coaxial with respect to the shaft elements 21, 22 (and therefore to the longitudinal axis X), for the insertion of a nut 33. Such a nut 33 ensures that the coupling between the shaft elements 21, 22 is maintained while pedalling.

0055The nut 33 is inserted into the through hole 31 and stops abutting with a radial flange 34 thereof against a washer 133 that, in turn, abuts with the inner wall of the shaft element 21, whereas the threaded shank 35 of the nut 33 screws into the threaded hole 32.

0056The nut 33 comprises a first portion 33a wherein a hole having a shaped inner surface is formed to receive a closing tool, in particular an allen spanner. The nut 33 also has a second portion 33b wherein a substantially cylindrical hole is formed.

0057Further details of the bottom bracket assembly described above are described in European patent application n° <patcit id="pcit0002" dnum="EP05026302A"><text>05026302</text></patcit> to the same Applicant, the content of which is incorporated herein by reference.

0058In accordance with the present invention, the bottom bracket assembly 1 of <figref idref="f0001">figure 1</figref> comprises a detection unit 100a of the torque applied to the shaft 23 by the cyclist while pedalling. Such a detection unit 100a comprises a battery 103, possibly of the rechargeable type, a signal generator consisting of one or more strain-gauges 101 associated with the nut 33, a processing unit 102 of the signal generated by the strain-gauges 101 and a transmission device of such a signal to the outside, comprising in particular an antenna 154.

0059Preferably, the strain-gauges 101 are arranged so as to constitute a strain-gauge bridge, in particular a known type of bridge that uses four resistances in the differential configuration, like for example a Wheatstone bridge. As shall be described better later on, the particular positioning of the resistances in the differential configuration allows a signal to be provided according to just the torsional deformations of the nut 33 with which the strain-gauges 101 are associated, i.e. not influenced by axial deformations due to traction or bending of the nut 33.

0060The strain-gauges 101 are fed by the electrical signal emitted by the battery 103 and act upon such a signal modifying it according to the torsional deformation of the nut 33, thus generating a modified electrical signal, in the form of current or voltage. Since the deformation of the nut 33 is proportional to the torque applied by the cyclist while pedalling, the electrical signal modified by the strain-gauges 101 shall also be proportional to such a torque.

0061The processing unit 102 is fed by the same battery 103, but alternatively it can contain its own dedicated battery.

0062The processing unit 102 is housed in the cylindrical hole of the second portion 33b of the nut 33. Alternatively, the processing unit 102 can be arranged outside of the nut 33, in a position adjacent to the battery 103.

0063The processing unit 102 processes the electrical signal generated by the strain-gauges 101 to then transmit it to the outside. By processing here is meant any operation carried out on the signal, for example a simple amplification.

0064The antenna 154 comes out from the processing unit 102, in the form of a cable, which ends on the outer edge of the cavity 21a of the shaft element 21. In this way, the signal transmitted by the antenna 154 is not shielded by the walls of the shaft element 21.

0065In the embodiment illustrated in <figref idref="f0001">figure 1</figref>, the signal processed by the processing unit 102 is sent to the outside by the antenna 154 through a radio frequency transmission. The processing unit 102 in this case comprises a RF transmitter associated with the antenna 154. The signal transmitted can be of the analogue type or, preferably, of the digital type, in which case an A/D converter is provided upstream of the RF transmitter.

0066<figref idref="f0002">Figure 1a</figref> shows in detail a block diagram of the embodiment of the detection unit 100a used in the bottom bracket assembly 1 of <figref idref="f0001">figure 1</figref>. In particular, the battery 103, the strain-gauges 101 connected in series to the battery 103, the processing unit 102 connected in series to the strain-gauges 101 and the antenna 154 coming out from the processing unit 102 are represented. The processing unit 102 comprises in particular an amplifier 200 of the signal generated by the strain-gauges 101, an A/D converter 201 and a RF transmitter 202, all fed by the battery 103.

0067<figref idref="f0002">Figure 1b</figref> shows in detail a block diagram of an alternative embodiment of the detection unit 100a that can be used in the bottom bracket assembly 1 of <figref idref="f0001">figure 1</figref>. For the sake of clarity of illustration, in <figref idref="f0002">figure 1b</figref> the power supply battery and the electrical power supply circuit associated with it have not been represented. Such a circuit and such a battery are, however, present and are totally identical to those illustrated in <figref idref="f0002">figure 1a</figref>.

0068The embodiment of <figref idref="f0002">figure 1b</figref> differs from the one illustrated in <figref idref="f0002">figure 1a</figref> in that it also comprises a cadence sensor 203 that supplies a signal proportional to the rotation speed of the shaft 23, and a processor 204, operatively arranged between the converter 201 and the RF transmitter 202, intended to receive both the cadence signal generated by the cadence sensor 203 and the torque signal generated by the strain-gauges 101 and suitably amplified by the amplifier 200 and digitalised by the A/D converter 201. The processor 204 analyses the torque signal to process it into a signal proportional to the power exerted by the cyclist. Preferably, the power signal is an average power signal and is transmitted to the outside of the detection unit 100a only at predetermined time intervals, to limit the consumption of the battery 103. Moreover, the cadence sensor 203 is only activated when there is a rotation of the shaft 23 and therefore it also acts as a switch of the detection unit 100a.

0069<figref idref="f0002">Figure 1c</figref> shows in detail a block diagram of an alternative embodiment of the detection unit 100a that can be used in the bottom bracket assembly 1 of <figref idref="f0001">figure 1</figref>. For the sake of clarity of illustration, in <figref idref="f0002">figure 1c</figref> the power supply battery and the electrical power supply circuit associated with it have not been represented. Such a circuit and such a battery are, however, present and are totally identical to those illustrated in <figref idref="f0002">figure 1a</figref>.

0070The embodiment of <figref idref="f0002">figure 1c</figref> differs from the one illustrated in <figref idref="f0002">figure 1a</figref> in that the processing unit 102 comprises a processor 205, operatively arranged between the converter 201 and the RF transmitter 202, which continuously receives the torque signal generated by the strain-gauges 101 and suitably amplified by the amplifier 200 and digitalised by the A/D converter 201. The processor 205 analyses this signal to calculate the pedalling cadence and therefore the average power developed by the cyclist. The power signal is transmitted to the outside through the antenna 154 only at predetermined time intervals.

0071Irrespective of the specific embodiment of the detection unit 100a, it can comprise a LED 310 (<figref idref="f0002">figure 1c</figref>) that indicates the operating state of the unit (for example, if it is active a signal transmission to the outside) and/or the charging state of the battery 103.

0072It is also possible to provide a switch 311 (<figref idref="f0002">figure 1c</figref>) between the battery 103 and the remaining part of the detection unit 100a. Such a switch can be manual and actuated by the cyclist when necessary, or else as already stated it could be associated with a cadence sensor (or more generally with a movement sensor) to be actuated in closure only when the bicycle moves. It is also foreseen the use of a switch (mechanical, proximity, a switch 312 of the reed type, illustrated in <figref idref="f0002">figure 1c</figref>, etc.) the actuation of which commands the start of the automatic calibration or diagnosis operations.

0073Again with reference to the embodiment illustrated in <figref idref="f0001">figure 1</figref>, the signal coming out from the detection unit 100a is transmitted by radio frequency, through the antenna 154, to other command/control systems associated with the bicycle. For example, the signal coming out from the detection unit 100a can be used by a cyclecomputer associated with the handlebars of the bicycle to be combined with a signal proportional to the instant value of the rotation speed of the shaft 23 and thus provide an instant power value exerted by the cyclist while pedalling.

0074The transmission of the signal coming out from the detection unit 100a to the other command/control systems provided in the bicycle can, however, take place according to different ways from that by radio frequency illustrated and described with reference to <figref idref="f0001">figures 1</figref>, <figref idref="f0002">1a, 1b and 1c</figref>.

0075For example, in the embodiment illustrated in <figref idref="f0003">figure 2</figref> the transmission of the signal coming out from the detection unit 100a takes place through the use of sliding contacts. In particular, on the outer surface of the shaft element 21 two or more circular pathways 206 (in the form of contact rings) are provided which are electrically insulated from one another and electrically connected to the processing unit 102. Close to the adaptor ring 3 corresponding sliding contacts 207 are positioned, made for example in the form of brushes, which make the electrical connection with the circular pathways 206 when the shaft element 21 is rotating. Two insulated wires 208 cross the adaptor ring 3 to carry the signal detected by the detection unit 100a to the outside. Apart from that, the embodiment illustrated in <figref idref="f0003">figure 2</figref> is totally identical to the one illustrated in <figref idref="f0001">figure 1</figref>.

0076In the embodiment illustrated in <figref idref="f0004">figure 3</figref>, the transmission of the signal coming out from the detection unit 100a, on the other hand, takes place through the use of solenoids. In particular, on the outer surface of the shaft element 21 a solenoid 209 is wound that is electrically connected to the processing unit 102. The solenoid 209 rotates as a single piece with the shaft element 21. At the adaptor ring 3 a corresponding fixed solenoid 210 is provided. The two solenoids 209 and 210 substantially define the primary and secondary windings of a transformer. The signal detected by the detection unit 100a is transmitted, through the solenoid 209, to the fixed solenoid 210 and from here transmitted, through two insulated wires 211 that cross the adaptor ring 3, to the outside. In this case, it is possible to foresee that in addition to transmit the signal detected by the detection unit 100a to the outside, the transformer is used in the opposite sense to supply power supply energy from the outside to the detection unit 100a. In the two wires 211 there shall therefore be both a torque signal and a power supply signal. The detection unit 100a shall in this case be provided with at least one storage element (for example, a condenser) of the energy coming from the outside. Apart from that, the embodiment illustrated in <figref idref="f0004">figure 3</figref> is totally identical to the one illustrated in <figref idref="f0001">figure 1</figref>.

0077Going back to the embodiment of <figref idref="f0001">figure 1</figref>, the strain-gauges 101, the processing unit 102 and the battery 103 (and therefore substantially the entire detection unit 100a) are all contained in a case 100 shaped to be inserted in the cavity 21a of the shaft element 21 of the right crank arm assembly 5 when this is already assembled on the bicycle. The transmission of the power supply energy and of the signals between the various elements of the detection unit 100a is carried out for example through cables.

0078The detection unit 100a has at least one interface surface not covered by the case 100 (and therefore exposed to the outside) on which the strain-gauges 101 are positioned, so that they can come into contact with the inner surface of the cylindrical hole of the second portion 33b of the nut 33. The surface of the strain-gauges 101 in contact with the inner surface of the cylindrical hole of the second portion 33b of the nut 33 has an adhesive substance that ensures the cohesion of the strain-gauge 101 with such a surface. The strain-gauges 101 must follow the deformation of the nut 33 while pedalling and therefore the adhesion between the strain-gauges 101 and the inner surface of the cylindrical hole of the second portion 33b of the nut 33 must be sufficiently strong.

0079Alternatively, the detection unit 100a can be associated with the nut 33 before it is used to assemble the bottom bracket assembly 1. In this case, firstly the strain-gauges 101 are applied to the inner surface of the cylindrical hole of the second portion 33b of the nut 33 an then they are connected with the processing unit 102 and with the battery 103. In this case an area for the insertion of an assembly tool, in particular an allen spanner, is provided in the nut 33.

0080The nut 33 fixedly connected to the detection unit 100a can be inserted from the right (with reference to <figref idref="f0001">figure 1</figref>), in order to be screwed into the threaded hole 32. Such screwing takes place by reaching from the left the inner grooved surface of the first portion 33a of the nut 33 with the assembly tool.

0081Alternatively, it is possible to mount the strain-gauges 101, instead of directly on the inner surface of the nut 33, on an intermediate support element (for example a rubber buffer) to be glued to the nut 33. In this case, the deformation of the nut 33 is transmitted to the strain-gauges 101 by means of such an intermediate support element, which must therefore be made from a material with physical characteristics with respect to the material from which the nut 33 is made such as to follow the deformations of the latter (i.e. it must not be rigid).

0082There is an alternative embodiment that is not illustrated in which the positioning of the detection unit 100a with respect to the bottom bracket assembly 1 is mirror-like the one illustrated in <figref idref="f0001">figure 1</figref>. In this embodiment, the case 100 can be inserted into the cavity 22a of the shaft element 22 associated with the left crank arm 18, and the nut 33 has the portion 33b with the substantially cylindrical hole at the shaft element 22 and the portion 33a with the inner surface shaped to receive the closing tool at the shaft element 21 associated with the right crank arm 17.

0083<figref idref="f0005">Figure 4</figref> shows an alternative embodiment of the bottom bracket assembly 1 of the present invention. In such a figure, elements corresponding to those illustrated in <figref idref="f0001">figure 1</figref> are indicated with the same reference numeral.

0084The embodiment illustrated in <figref idref="f0005">figure 4</figref> differs from the one illustrated in <figref idref="f0001">figure 1</figref> for the different arrangement of the detection unit 100a and in that it uses a replaceable and possibly rechargeable battery 103. Indeed, it should be noted that the battery 103 is no longer fixedly associated with the processing unit 102 and with the strain-gauges 101, but can be connected to them through connectors 106 (for example male connectors) that transport the power supply energy both to the strain-gauges 101 and to the processing unit 102. For this purpose, the processing unit 102 comprises connectors 104 (for example female connectors) intended to cooperate with the connectors 106 of the battery 103. The exchange of signals between strain-gauges 101 and processing unit 102, on the other hand, continues to take place preferably via cables, so as to avoid the signal can be dispersed, due to the low order of magnitude of the signal (typically microvolts) supplied by the strain-gauges 101, as would happen if the signal were transmitted through connectors.

0085The battery 103 is housed in a casing 105. In order to avoid infiltrations of humidity or dirt that could oxidise the connectors 104, 106, it is optionally foreseen to use gaskets 151, for example in the form of O-rings, arranged between the casing 105 and the inner surface of the shaft element 22. The number of gaskets (two in <figref idref="f0005">figure 4</figref>) and the position with respect to the shaft element 22 can be different to what is illustrated in <figref idref="f0005">figure 4</figref>.

0086The use of a battery 103 provided with connectors, like the one illustrated in <figref idref="f0005">figure 4</figref>, is advantageous since it allows the battery to be changed once it has run out.

0087Regarding the constructive characteristics inherent to the bottom bracket assembly 1, what has been stated with reference to the embodiment of <figref idref="f0001">figure 1</figref> applies also to <figref idref="f0005">figure 4</figref>, with the sole difference that the nut 33 has the first portion 33a with the substantially cylindrical hole at the shaft element 22 associated with the left crank arm 18 and the second portion 33b with the hole having an inner surface shaped to receive the closing tool (at the shaft element 21 associated with the right crank arm 17).

0088There is an alternative embodiment that has not been illustrated in which the positioning of the detection unit 100a with respect to the bottom bracket assembly 1 is mirror-like the one illustrated in <figref idref="f0005">figure 4</figref>, i.e. the battery 103 can be inserted in the cavity 21a of the shaft element 21 associated with the right crank arm 17, and the nut 33 has the portion 33b with the substantially cylindrical hole at the shaft element 21 and the portion 33a with the inner surface shaped to receive the closing tool at the shaft element 22 associated with the left crank arm 18, substantially as illustrated in <figref idref="f0001">figure 1</figref>.

0089<figref idref="f0006">Figure 5</figref> shows an alternative embodiment of the bottom bracket assembly 1 of the present invention. In such a figure, elements corresponding to those illustrated in <figref idref="f0001">figure 1</figref> are indicated with the same reference numeral.

0090The embodiment illustrated in <figref idref="f0006">figure 5</figref> differs from the one illustrated in <figref idref="f0001">figure 1</figref> in that an additional power supply device (typically a battery) 107 in the form of a cartridge is provided, wherein this additional power supply device can be inserted at the shaft element 22 associated with the left crank arm 18. The additional battery 107 comprises male connectors 105b that cross the inside of the nut 33 to connect with the female connectors 105a of the battery 103.

0091Such a solution is advantageous when the bicycle is intended to be used for a long time. Indeed, it allows the autonomy of the detection unit 100a to be increased.

0092There is an alternative embodiment that has not been illustrated in which the positions of the battery 103 and of the additional battery 107 are reversed, the battery 103 being provided at the shaft element 22 associated with the left crank arm 18 and the additional battery 107 being provided at the shaft element 21 associated with the right crank arm 17.

0093<figref idref="f0007">Figure 6</figref> shows an alternative embodiment of the bottom bracket assembly 1 of the present invention. In such a figure, elements corresponding to those illustrated in <figref idref="f0001">figure 1</figref>, <figref idref="f0005">4</figref> and <figref idref="f0006">5</figref> are indicated with the same reference numeral.

0094The embodiment illustrated in <figref idref="f0007">figure 6</figref> differs from the one illustrated in <figref idref="f0005">figure 4</figref> in that an additional battery 107 in the form of a cartridge is provided, wherein this additional battery can be inserted at the shaft element 21 associated with the right crank arm 17. The additional battery 107 comprises male power connectors 105b that cross the inside of the nut 33 to connect to the female connectors 105a of the battery 103. Such a solution has the same advantages as the solution illustrated in <figref idref="f0006">figure 5</figref>.

0095There is an alternative embodiment that has not been illustrated in which the positions of the battery 103 and of the additional battery 107 are reversed, the battery 103 being provided at the shaft element 21 associated with the right crank arm 17 and the additional battery 107 being provided at the shaft element 22 associated with the left crank arm 18, substantially as illustrated in <figref idref="f0006">figure 5</figref>.

0096<figref idref="f0008">Figure 7</figref> shows an alternative embodiment of the bottom bracket assembly 1 of the present invention. In such a figure, elements corresponding to those illustrated in <figref idref="f0001">figure 1</figref> are indicated with the same reference numeral.

0097The embodiment illustrated in <figref idref="f0008">figure 7</figref> differs from the one illustrated in <figref idref="f0001">figure 1</figref> in that the processing unit 102 is outside of the nut 33 and fixedly connected to the battery 103. Also in this case, the battery 103 and the processing unit 102 are housed in the case 100 that can be inserted in the cavity 21a of the shaft element 21 associated with the right crank arm 17.

0098The strain-gauges 101, on the other hand, are in this case positioned on the outer surface of the shaft element 21, at an area where the wall of the shaft element 21 is thinner. Alternatively, the strain-gauges 101 can be associated with the inner surface of the shaft element 21, at the same area.

0099There is an alternative embodiment that has not been illustrated in which the position of the detection unit 100a is mirror-like the one illustrated in <figref idref="f0008">figure 7</figref>, i.e. with the components of the detection unit 100a associated with the shaft element 22 associated with the left crank arm 18.

0100<figref idref="f0009">Figure 8</figref> illustrates a further embodiment of the bottom bracket assembly 1 of the present invention. In such a figure, elements corresponding to those illustrated in <figref idref="f0001">figure 1</figref> are indicated with the same reference numeral.

0101The embodiment of <figref idref="f0009">figure 8</figref> differs from the one of <figref idref="f0001">figure 1</figref> in that the battery 103, the processing unit 102 and the strain-gauges 101 are housed in a cavity 17a of the right crank arm 17. Preferably the aforementioned elements are housed in an area of such a cavity close to the coupling end of the crank arm 17 with the shaft element 21, so as to safeguard the inertia of the crank arm 17 and detect greater tension values. In this case the bending deformation of the crank arm 17 is mainly detected, from which it is in any case possible to calculate the torque applied by the cyclist. The cavity 17a of the crank arm 17 could be made so as to be open in a first assembly step and then be closed with a cover after the detection unit 100a has been introduced into the cavity.

0102There is an alternative embodiment in which the detection unit 100a is housed in the left crank arm 18.

0103<figref idref="f0010">Figure 9</figref> illustrates a further embodiment of the bottom bracket assembly 1 of the present invention. In such a figure, elements corresponding to those illustrated in <figref idref="f0001">figures 1</figref> and <figref idref="f0009">8</figref> are indicated with the same reference numeral.

0104The embodiment of <figref idref="f0010">figure 9</figref> differs from that of <figref idref="f0009">figure 8</figref> in that here the heavier elements of the detection unit 100a, i.e. the battery 103 and possibly also the processing unit 102, are housed in the cavity 21a of the shaft element 21, so as to safeguard the inertia of the crank arm 17, whereas the strain-gauges 101 are housed in the cavity 17a of the right crank arm 17, or possibly also on the outer surface thereof, to measure mainly the bending deformation thereof.

0105Preferably, as illustrated in <figref idref="f0010">figure 9</figref>, the position of the strain-gauges 101 is closer to the shaft element 21 than to the pedal.

0106In all of the embodiments described above, it is possible to use a rechargeable battery 103, preferably of the type that is rechargeable by induction. In this case, to carry out recharging it shall be sufficient to bring the recharging instrument close to the bicycle without needing to provide external connectors, which would create insulation problems. An embodiment of a detection unit 100a that uses a battery that is rechargeable by induction is illustrated in <figref idref="f0011">figure 10</figref>. In such an embodiment, a battery-charger 152 is inserted into a seat 153 formed in the battery 103. In another embodiment that has not been illustrated, a photovoltaic cell is used suitable for cooperating with the battery 103.

0107Moreover, in all of the embodiments described above the strain-gauges 101 can be applied directly onto one of the shaft elements 21, 22. The positioning of the strain-gauges 101 on the shaft element is done in a way which is suitably to solve measurement problems that arise due to the particular operation of the bicycle.

0108<figref idref="f0012">Figure 11</figref> illustrates in a very schematical way the tensions t that are generated in the various areas of a shaft 23 when it is subjected to a torque. It should be noted how the areas in which there is greater concentration of tension are those at the thinner walls of the shaft 23. These areas are the preferred areas for the positioning of the strain-gauges.

0109However, it must be considered that the tension generated on the shaft, and therefore the deformation that can be detected with the strain-gauges, does not just depend upon the torque, but also upon the bending and the dilation due to temperature variations and/or axial forces. In particular, the deformation stresses of the shaft are not constant, but have maximum and minimum values according to the angular position of the crank arms. As known, indeed, the cyclist exerts the maximum thrust upon the crank arms when they are in the area between the vertical position with the crank arm on top and the horizontal position with the crank arm in front. in addition, it must be considered that the only crank arm that transmits a torque to the shaft is the left crank arm, due to the fact that the right crank arm transmits the torque directly to the front sprocket with which it is coupled (such a front sprocket is indicated with 500 in <figref idref="f0009">figures 8</figref> and <figref idref="f0010">9</figref>). The front sprocket in turn transmits the torque to the rear wheel through the chain. It must also be considered that both of the crank arms generate a bending stress on the shaft; the strain-gauges shall thus detect a deformation even when in reality there is no torque applied by the cyclist.

0110Consider for example the case in which, instead of the four strain-gauges illustrated in <figref idref="f0002">figures 1a, 1b and 1c</figref> connected together in a Wheatstone bridge, a single strain-gauge is used. Such a strain-gauge is advantageously associated with the shaft 23 in an angular position corresponding to the one in which the neutral axis of the shaft is located with respect to the crank arms 17, 18 when they are at 45° with respect to the horizontal direction. The position of the neutral axis is indicated with Z in <figref idref="f0012">figure 12b</figref>, and different examples of the angular position in which the strain-gauge can be positioned are illustrated by the signs A in <figref idref="f0012">figures 12a, 12c</figref> and <figref idref="f0013">12d</figref>, which schematically represent the position of the crank arms 17, 18 in three different operative conditions, i.e. respectively at the moment when the cyclist starts thrusting on the pedals, in the maximum thrusting step and at the moment when he stops thrusting on the pedals. As illustrated in <figref idref="f0012">figure 12a</figref>, it is possible to assume an angular tolerance area α with respect to the ideal one indicated by the dark circles, where α is preferably equal to 90°.

0111Then considering the particular shape of the strain-gauge, it is advantageous to position it on the shaft 23 at an angular interval of size β, where β is preferably between 40° and 50°, and more preferably equal to 45°, as illustrated in <figref idref="f0013">figure 13</figref>. Indeed, when the cyclist pushes upon the left crank arm 18 transmitting the torque M to the shaft 23, the latter deforms being subjected to an elongation in the direction of the arrow S1 and a contraction in the direction of the arrow S2, for which reason it is advantageous to orientate the strain-gauge 101 with its direction of deformation according to arrow S1 so that the magnitude of the detected signal is as large as possible.

0112<figref idref="f0014">Figures 14a and 14b</figref> illustrate alternative positionings of the strain-gauge 101 to detect a signal representative of the torque on the shaft 23 that is influenced as little as possible by bending stress. In such figures it should be noted how, when at a crank arm, for example the right crank arm 17, the bending deformation F is at its maximum value, and at the other crank arm, for example the left crank arm 18, such a deformation is zero. Then considering that the torque M is only present on the shaft 23 when the cyclist pushes upon the left crank arm 18, it is possible to obtain a signal proportional to just the torque exerted upon the shaft 23 by positioning a single strain-gauge 101 at the right bearing 13 (<figref idref="f0014">figure 14b</figref>) and only detecting the signal when a cadence sensor (or position or movement sensor) indicates that the left crank arm 18 is in a thrusting position (i.e. within the angular range of size α of <figref idref="f0012">figure 12a</figref>), and preferably in the maximum thrust position. However, it is considered acceptable to position the strain-gauge 101 at an axial distance x from the bearing 13 of between 0 and 20 mm. Alternatively, a strain-gauge can be positioned at each bearing, as schematically illustrated in <figref idref="f0014">figure 14a</figref>, by exploiting the cadence signal to determine the position of the crank arms 17, 18 and subtract the signal detected by the strain-gauge 101 positioned at the right bearing 13 when the cyclist pushes upon the right crank arm 17 from the signal detected by the strain-gauge 101 positioned at the left bearing 14 when the cyclist pushes upon the left crank arm 18.

0113Let us now consider the case in which two strain-gauges are used. As illustrated in <figref idref="f0015">figure 15a</figref>, the two strain-gauges 101 can be positioned on the shaft 23 in any angular position and at any axial position, orientating the two strain-gauges so that the respective directions of deformation are perpendicular to one another. In this way possible contributions caused by bending and/or traction stresses are eliminated with a differential measurement. By connecting the two strain-gauges according to a classic ½ bridge scheme, the difference between the signal generated by the first strain-gauge and that generated by the second strain-gauge is proportional to just the torque applied to the shaft 23.

0114In an alternative configuration that has not been illustrated, the two strain-gauges are not one on top of the other like in <figref idref="f0015">figure 15a</figref>, but are associated with the shaft at diametrically opposite areas.

0115A particularly preferred configuration is, however, the one illustrated in <figref idref="f0015">figure 15b</figref>, in which two pairs of strain-gauges 101 are used, these being connected according to a Wheatstone bridge scheme, the same one illustrated in <figref idref="f0002">figures 1a-1c</figref>. In this configuration, advantageously, the detected signal is of a magnitude greater than the one detected with the configuration of <figref idref="f0015">figure 15a</figref>.

0116In an alternative embodiment of the detection unit 100a of the bottom bracket assembly 1 of the present invention, instead of the strain-gauges a piezoelectric element is used, i.e. an element capable of generating a potential difference when subjected to a pressure. Such an element therefore acts both as an energy source and as a signal generator. If the piezoelectric element is thus positioned so as to be compressed when the cyclist pushes upon the left crank arm, the potential difference obtained is a signal directly proportional to such a torque applied by the cyclist to the shaft of the bottom bracket assembly.

0117Since the magnitude of the energy produced by the piezoelectric element is not high, an additional battery is preferably used to supply possible electronic parts like the possible amplifier, A/D converter, and RF transmitter of <figref idref="f0002">figures 1a-1c</figref>.

0118<figref idref="f0016">Figure 16</figref> shows a first embodiment of the bottom bracket assembly 1 of the present invention in which a detection unit 100a comprising a piezoelectric element 301 is used. In particular, the piezoelectric element 301 is arranged between the matching surfaces of the teeth of the front toothings (preferably of the Hirth type) provided at the end portions 29, 30 of the shaft elements 21, 22. More specifically, the piezoelectric element 301 is housed in a suitable seat 301a formed, for example, by reducing the size of a tooth. It is also possible to see the processing unit 102 of the signals detected by the piezoelectric element 301 and the battery 103, which in this case supplies just the processing unit 102.

0119The processing unit 102 and the battery 103 are housed in the cavity 21a of the shaft element 21. The processing unit 102 can be of the type illustrated in <figref idref="f0002">figures 1a-1c</figref>.

0120In an alternative embodiment of the detection unit 100a, illustrated in <figref idref="f0017">figures 17</figref> and <figref idref="f0018">18</figref>, the piezoelectric element 301 is housed between the matching surfaces of the teeth of the front coupling toothings of the shaft element 22 and the crank arm 18, whereas the processing unit 102 and the battery 103 are housed in the cavity 22a of the shaft element 22.

0121In the embodiments of <figref idref="f0016 f0017 f0018">figure 16-18</figref>, the signal generated by the piezoelectric element 301 is directly proportional to the pressure exerted upon the outer surface of the piezoelectric element, which is in turn directly proportional to the torque applied to the shaft element 22 by the cyclist who pushes upon the pedal of the left crank arm 18. The signal coming out from the processing unit 102 is therefore proportional to the torque applied by the cyclist to the shaft (or to the shaft element) of the bottom bracket assembly.

0122According to a further alternative embodiment of the detection unit 100a, illustrated in <figref idref="f0019">figure 19</figref>, the piezoelectric element 301, the battery 203 and the processing unit 102 are embedded in the body of the crank arm, which in this case is preferably made from molten composite material, for example carbon fibre. Alternatively, the aforementioned elements can be inserted into suitable pockets (not illustrated) made in the body of the crank arm. The orientation of the piezoelectric element is such that it is subjected to pressures on upper and lower surfaces thereof due to the compression to which the areas of the body of the crank arm are subjected while pedalling. Also such pressures have a value proportional to the torque imparted by the cyclist while pedalling.

0123The detected deformation signal could alternatively also be used as a warning signal to indicate that the crank arm needs to be changed because it has been subjected to a deformation too big (for example above a predetermined threshold value) and could therefore start to wear.

0124<figref idref="f0020">Figure 20</figref> illustrates a further embodiment of the bottom bracket assembly 1 of the present invention, in which the piezoelectric element consists of the washer 133 arranged between the radial flange 34 of the nut 33 and the inner wall of the shaft element 21. Such a washer 133 can thus be made from piezoelectric material. By means of the particular geometry of the Hirth toothing provided at the end portions 29, 30 of the shaft elements 21, 22, the transfer of torque from one shaft element to the other generates a separation thrust in the axial direction of the two shaft elements, for which reason the washer 133 is compressed against the radial flange 34 of the nut 33.

0125The invention has up to now been described with reference to a mobile component of a bicycle. In reality the man skilled in the art shall have no difficulty in understanding that it can also be applied to fixed components like, for example, the frame, the seat post or the handlebars of the bicycle. In this case the detection unit detects the passage from a first tensional state to a second tensional state of the component and the generated signal can be used for example as an alarm signal to the reaching of critical tensions or to indicate that it is necessary to replace the component.

0126<figref idref="f0021">Figure 21</figref> illustrates for example a bicycle 400 in which the areas of various components of the bicycle in which it is possible to associate the detection unit 100a are highlighted. As illustrated, such a unit can be associated with the crank arm 17, for example at an area B thereof, with the shaft 23 of the bottom bracket assembly, for example in an area C thereof, with the frame 401 of the bicycle, for example in an area D thereof, with the seat post 402, for example in an area E thereof, with the handlebars 403, for example in an area F thereof, with the hub 404 of the wheel 405, for example in an area G thereof, with the rim 406 of the wheel 405, for example in an area H thereof, etc.

0127The invention has also always been described with reference to an electrical energy source (battery or piezo-electric crystal) and to a generator of an electrical signal varied according to the stress imparted upon the component (piezo-electric crystal itself or strain-gauge). However, other types of source and signals can be used. For example, it is possible to use a magnetic or electromagnetic field source and a variator of such a field. Preferably, the power supply signal and the representative signal are of the same type (for example, electrical signals), but the case in which such signals are of different types (for example, electrical and magnetic signals) is not excluded.

0128The man skilled in the art shall recognise that it is possible to combine the various characteristics of the embodiments described above to obtain further embodiments, all of which are in any case covered by the present invention as defined by the subsequent claims.