Bicycle axle assembly including a power meter

An axle assembly for a bicycle includes an axle having an inner wall extending along a length of the axle between a first end and a second end of the axle. The inner wall at least partially defines a first volume and a second volume within the axle. The first volume has a first diameter, and the second volume has a second diameter that is greater than the first diameter. The first volume is closer than the second volume to the first end of the axle. The axle assembly also includes a sensor attached to the inner wall of the axle within the second volume of the axle.

BACKGROUND

1. Field of the Disclosure

The present disclosure is generally directed to an axle assembly for a bicycle, and more particularly, to an axle assembly including a power meter.

2. Description of Related Art

A power meter for a bicycle determines power output by a rider of the bicycle. The power meter includes a strain gauge that measures torque applied to a component of the bicycle on which the strain gauge is positioned. For example, the power meter may be a crank-based power meter that includes a strain gauge that is positioned on an outer surface of the spindle. The crank-based power meter measures torque applied to a spindle. For such a crank-based power meter, the power output by the rider may be calculated based on the measured torque and an angular velocity of the spindle.

SUMMARY

In one example, an axle assembly for a bicycle includes an axle having an inner wall extending along a length of the axle between a first end and a second end of the axle. The inner wall at least partially defines a first volume and a second volume within the axle. The first volume has a first diameter, and the second volume has a second diameter that is greater than the first diameter. The first volume is closer than the second volume to the first end of the axle. The axle assembly also includes a sensor attached to the inner wall of the axle within the second volume of the axle.

In one example, the axle assembly further includes a sensor assembly. The sensor assembly includes a fixed portion. The fixed portion includes the sensor, and at least part of the fixed portion is positionally fixed relative to the axle. The sensor of the fixed portion of the sensor assembly is disposed entirely within the second volume of the axle.

In one example, the sensor assembly further includes a removable portion. The removable portion is removably attachable and electrically connectable to the fixed portion. At least part of the removable portion of the sensor assembly is disposed within the first volume of the axle.

In one example, the sensor assembly is a power meter, and the sensor is a strain gauge.

In one example, the strain gauge is a first strain gauge. The fixed portion of the sensor assembly further includes a second strain gauge. The first strain gauge and the second strain gauge are attached to the inner wall within the second volume of the axle, such that the first strain gauge and the second strain gauge are opposite each other.

In one example, the removable portion of the sensor assembly includes a power source electrically connectable to the first strain gauge and the second strain gauge.

In one example, the fixed portion of the sensor assembly further includes a circuit board electrically connected to the first strain gauge and the second strain gauge. The power source is electrically connected to the first strain gauge and the second strain gauge via the circuit board.

In one example, the fixed portion of the sensor assembly further includes a memory electrically connected to the circuit board. The memory is configured to store calibration data for the sensor assembly.

In one example, the fixed portion of the sensor assembly further includes an analog-to-digital (A/D) converter supported by the circuit board, the A/D converter is in communication with the first strain gauge and the second strain gauge. The first strain gauge is configured to generate a first analog signal, and the second strain gauge is configured to generate a second analog signal. The first analog signal and the second analog signal are analog representations of strain on the axle, respectively. The A/D converter is configured to convert the first analog signal to a first digital signal, convert the second analog signal to a second digital signal, generate a third digital signal that is based on the first analog signal and the second analog signal, or any combination thereof. The first digital signal, the second digital signal, and the third digital signal are digital representations of strain on the axle, respectively. The fixed portion of the sensor assembly is configured to transmit the first digital signal, the second digital signal, the third digital signal, or any combination thereof to the removable portion of the sensor assembly when the removable portion of the sensor assembly is electrically connected to the fixed portion of the sensor assembly.

In one example, the fixed portion of the sensor assembly further includes an amplifier in communication with the first strain gauge and the second strain gauge. The first strain gauge is configured to generate a first analog signal, and the second strain gauge is configured to generate a second analog signal. The first analog signal and the second analog signal are analog representations of strain on the axle, respectively. The amplifier is configured to amplify the first analog signal to a first amplified analog signal, amplify the second analog signal to a second amplified analog signal, amplify a signal based on the first analog signal and the second analog signal to a third amplified analog signal, or any combination thereof. The fixed portion of the sensor assembly is configured to transmit the first amplified analog signal, the second amplified analog signal, the third amplified analog signal, or any combination thereof to the removable portion of the sensor assembly when the removable portion of the sensor assembly is electrically connected to the fixed portion of the sensor assembly.

In one example, the fixed portion of the sensor assembly includes a radially expandable applicator attached to the first strain gauge and the second strain gauge. The radially expandable applicator is operable to move the first strain gauge and the second strain gauge radially outwards until the first strain gauge and the second strain gauge are physically connected to the inner wall.

In one example, the fixed portion of the sensor assembly further includes a first layer of adhesive disposed on the first strain gauge and a second layer of adhesive disposed on the second strain gauge. The first strain gauge and the second strain gauge are attached to the inner wall of the axle via the first layer of adhesive and the second layer of adhesive, respectively.

In one example, the fixed portion of the sensor assembly further includes a first layer of material having a first side and a second side opposite the first side. The first side of the first layer of material is attached to the radially expandable applicator, and the second side of the first layer of material is attached to the first strain gauge. A second layer of material has a first side and a second side opposite the first side. The first side of the second layer of material is attached to the radially expandable applicator, and the second side of the second layer of material is attached to the second strain gauge.

In one example, the first layer of material and the second layer of material are made of rubber or silicon.

In one example, the fixed portion of the sensor assembly further includes a base attached to the inner wall of the axle. The radially expandable applicator is physically connected to the base, such that a depth of the radially expandable applicator relative to the first end of the axle is fixed and a clocking of the radially expandable applicator is fixed relative to the inner wall.

In one example, a crankset for a bicycle includes an axle having an inner wall extending along a length of the axle between a first end and a second end of the axle. The inner wall at least partially defines a first volume and a second volume within the axle. The first volume has a first diameter, and the second volume has a second diameter that is greater than the first diameter. The first volume is closer than the second volume to the first end of the axle. The crankset also includes a first arm attached to the axle at the first end of the axle, a second arm attached to the axle at the second end of the axle, at least one crank attached to the first arm or the second arm, and a sensor assembly. The sensor assembly includes a fixed portion. At least part of the fixed portion is positionally fixed relative to the inner wall of the axle. The fixed portion includes a sensor that is attached to the inner wall of the axle within the second volume of the axle.

In one example, the sensor is a first strain gauge. The fixed portion of the sensor assembly further includes a second strain gauge. The first strain gauge and the second strain gauge are attached to the inner wall within the second volume of the axle, such that the first strain gauge and the second strain gauge are opposite each other.

In one example, the fixed portion of the sensor assembly further includes a radially expandable applicator operable to move the first strain gauge and the second strain gauge radially outwards into contact with the inner wall. The first strain gauge and the second strain gauge each have a first side and a second side opposite the first side. The fixed portion of the sensor assembly also includes a first layer of material having a first side and a second side opposite the first side. The first side of the first layer of material is attached to the radially expandable applicator, and the second side of the first layer of material is attached to the first side of the first strain gauge. The fixed portion of the sensor assembly includes a second layer of material having a first side and a second side opposite the first side. The first side of the second layer of material is attached to the radially expandable applicator, and the second side of the second layer of material is attached to the first side of the second strain gauge. The fixed portion of the sensor assembly also includes a first layer of adhesive disposed on the second side of the first strain gauge and a second layer of adhesive disposed on the second side of the second strain gauge. The first strain gauge and the second strain gauge are attached to the inner wall of the axle via the first layer of adhesive and the second layer of adhesive, respectively.

In one example, the sensor assembly further includes a removable portion that is removably attachable and electrically connectable to the fixed portion of the sensor assembly.

In one example, an axle for a bicycle includes an inner wall extending along a length of the axle between a first end and a second end of the axle. The inner wall at least partially defines a first volume and a second volume within the axle. The first volume has a first diameter, and the second volume has a second diameter that is greater than the first diameter. The first volume is closer than the second volume to the first end of the axle. The axle also includes a first sensor attached to the inner wall within the second volume, and a second sensor attached to the inner wall within the second volume. The second sensor is opposite the first sensor.

DETAILED DESCRIPTION OF THE DISCLOSURE

For crank-based power meters of the prior art, the strain gauge is positioned on an external diameter of the spindle. Such positioning exposes the strain gauge to possible damage during installation of the crank on the bicycle and exposes the strain gauge to the environment. Further, crank-based power meters of the prior art are charged by plugging the entire bicycle into an electrical power outlet. The present disclosure provides examples of axle assemblies and crank-based power meters that solve or improve upon one or more of the disadvantages described above with prior known power meters.

A bicycle axle assembly of the present embodiments includes an axle (e.g., a spindle) in which strain gauges are disposed. The strain gauges are attached to an inner surface of the spindle, such that the strain gauges are protected from the environment and damage during crank installation. By mounting the strain gauges inside the spindle, the spindle does not require a hole through which gauge signal and power wires may pass.

The strain gauges are part of a sensor assembly (e.g., a power meter) that includes a fixed portion and a removable portion. The fixed portion, at least part of which is positionally fixed relative to the axle, includes the strain gauges, and the removable portion includes a power source that powers the strain gauges. The removable portion may be removed from the bicycle for charging, such that the entire bicycle does not need to be plugged into an electrical power outlet to charge the sensor assembly.

Turning now to the drawings,FIG. 1illustrates an example of a human powered vehicle50that may include the disclosed axle assembly. InFIG. 1, the human powered vehicle50is a first type of bicycle, such as a road bicycle. While the bicycle50depicted inFIG. 1is a road bicycle (e.g., with mechanical (cable, hydraulic, and/or pneumatic) or non-mechanical (wired and/or wireless) drive systems), the axle assembly, including the specific embodiments and examples disclosed herein as well as alternative embodiments and examples, may be implemented on other types of vehicles or bicycles. For example, the disclosed axle assembly may be used on other types of two-, three-, and four-wheeled human powered vehicles such as, for example, a mountain bicycle (e.g., with full or partial suspensions), as well.

The bicycle50includes a frame52, a front wheel54, and a rear wheel56each rotatably attached to the frame52, and a drivetrain58. A front brake60is provided for braking the front wheel54, and a rear brake62is provided for braking the rear wheel56. The bicycle50also generally has a seat64near a rear end of the frame52and carried on an end of a seat tube66connected to the frame52. The bicycle50also has handlebars68near a forward end of the frame52. The handlebars68are attached to the frame52for user, or rider, control of the bicycle50. A brake lever70is carried on the handlebars68for actuating one of the front brake60or rear brake62, or both. If the brake lever70actuates only the front brake60or the rear brake62, a second brake lever (not shown) may also be provided to actuate the other brake. A front and/or forward riding direction or orientation of the bicycle50is indicated by the direction of the arrow A inFIG. 1. As such, a forward direction for the bicycle50is indicated by the direction of arrow A.

The drivetrain58has a chain C and a front sprocket assembly72, which is coaxially mounted with a crank assembly74having pedals76. The front sprocket assembly72and at least a portion of the crank assembly74(e.g., excluding the pedals76) form a crankset77. The drivetrain58also includes a rear sprocket assembly78coaxially mounted with the rear wheel56and a rear gear change mechanism, such as a rear derailleur80.

As is illustrated inFIG. 1, the front sprocket assembly72may include one or more coaxially mounted chain rings, gears, or sprockets. In the example ofFIG. 1, the front sprocket assembly72has two such sprockets, F1and F2, each having teeth82around a respective circumference. In the example ofFIG. 2, the front sprocket assembly72has one such sprocket F1, having teeth82around a circumference of the sprocket F1. As is illustrated inFIG. 1, the rear sprocket assembly78may include a plurality of coaxially mounted gears, cogs, or sprockets G1-GN (e.g., eleven sprockets). Each sprocket G1-GN also has teeth84arranged around a respective circumference. Referring toFIG. 1, the number of teeth82on the smaller diameter front sprocket F2may be less than the number of teeth82on the larger diameter front sprocket F1. The number of teeth84on the rear sprockets G1-GN may gradually decrease from the largest diameter rear sprocket G1to the smallest diameter sprocket GN. As shown inFIG. 1, a front gear changer85may be operated to move from a first operating position to a second operating position to move the chain C between the front sprockets F1and F2. Likewise, the rear derailleur80may be operable to move between a number of different operating positions (e.g., eleven operating positions) to switch the chain C to a selected one of the rear sprockets G1-GN. In an embodiment, the rear sprocket assembly78may have more or fewer sprockets. For example, in an embodiment, a rear sprocket assembly may have twelve or thirteen sprockets. Dimensions and configuration of the rear derailleur80may be modified to accommodate a specific implemented plurality of sprockets. For example, an angle and length of the linkage and/or the configuration of the cage of the rear derailleur80may be modified to accommodate specific sprocket combinations.

The rear derailleur80is depicted in these examples as a wireless, electrically actuated rear derailleur mounted or mountable to the frame52, or frame attachment, of the bicycle50. The electric rear derailleur80has a base member86(e.g., a b-knuckle) that is mounted to the bicycle frame52. A linkage88has two links L that are pivotally connected to the base member86at a base member linkage connection portion. A movable member90(e.g., a p-knuckle) is connected to the linkage88. A chain guide assembly92(e.g., a cage) is configured to engage and maintain tension in the chain and is pivotally connected to a part of the movable member90. The cage92may rotate or pivot about a cage rotation axis in a damping direction and a chain tensioning direction.

A motor module is carried on the electric rear derailleur80and has a battery. The battery supplies power to the motor module. In one example, the motor module is located in the movable member90. However, the motor module may instead be located elsewhere, such as in one of the links L of the linkage88or in the base member86. The motor module may include a gear mechanism or transmission. As is known in the art, the motor module and gear mechanism may be coupled with the linkage88to laterally move the cage92and thus switch the chain C among the rear sprockets on the rear sprocket assembly78.

The battery may instead be an alternate power supply or power source and may operate other electric components of the bicycle50within a linked system. In one example, the battery alone powers all electric components of the bicycle50(e.g., a drive motor for an electrically powered bicycle), including the rear derailleur80. In other examples, multiple power supplies, which may collectively or individually power the electric components of the system, including the rear derailleur80, may be provided. Additional batteries or other power supplies may be attached to the rear derailleur80or located at other positions, such as the frame52. In this example, however, the battery is configured to be attached directly to the rear derailleur80, and to provide power to the components of the rear derailleur80. In an embodiment, the rear derailleur is configured such that the battery provides power to only the components of the rear derailleur80.

A control device100is mounted to the handlebars68for wirelessly actuating the motor module and operating the rear derailleur80for executing gear changes and gear selection. Multiple control devices100may be used with the bicycle50. In other embodiments, the control device100may be located in other locations on the bicycle50or, alternatively, may be distributed among various components of the bicycle50, with routing of a communication link to accommodate necessary signal and power paths. The control device100may also be located in places other than on the bicycle50, such as, for example, on a rider's wrist or in a jersey pocket. The communication link may include wires, may be wireless, or may be a combination thereof. In one example, the control device100may be integrated with the rear derailleur80to communicate control commands between components. The control device100may include a processor, a communication device (e.g. a wireless communication device), a memory, and one or more communication interfaces.

The handlebars68ofFIG. 1illustrates a drop bar assembly; however, the control device100may be used with other types of handlebar assemblies as well, such as an aero-bar configuration, bullhorn bars, riser bars, or any other type of bicycle handlebar. Also, while the embodiments described herein describe control devices attached to handlebars, a person having experience in the art would recognize the possible positioning of control devices100at other areas of the bicycle50, such as locations throughout the frame52.

The control device100is configured to actuate or otherwise control components of the bicycle50. For example, the control device100may be configured to control gear shifting of the front gear changer85and/or the rear derailleur80. The control device100may also receive and/or send data to one or more components of the bicycle. For example, the control device100may be configured to receive data from one or more sensors of an axle assembly of the crankset77. For example, the control device100may be configured to receive data from a power meter included within the axle assembly of the crankset77.

Referring toFIGS. 2-4, the crankset77includes a housing120(e.g., a bracket or bottom bracket), one or more sprockets F (e.g., a chainring drive sprocket; the sprocket F1), a first arm122(e.g., a first crank or crankarm) connected to the bracket120at or adjacent to a first end124of the bracket120, and a second arm126(e.g., a second crank or crankarm) connected to the bracket120at or adjacent to a second end128of the bracket120opposite the first end124of the bracket120.FIGS. 2-4show a single sprocket F. In other embodiments, the crankset77includes more than one sprocket F1(e.g., two sprockets F, as shown inFIG. 1).

The bracket120, and thus, the crankset77, is attachable to the frame52of the bicycle50in any number of ways including, for example, via pressing into a corresponding opening in the frame52of the bicycle or via a threaded connection between the bracket120and the frame52. The bracket120is attached to the frame52, such that the bracket120is positionally fixed relative to the frame52. The bracket120may be made of any number of materials including, for example, steel or a ceramic.

The bracket120is hollow and houses a number of components (seeFIGS. 5 and 11-13). For example, the bracket120houses at least an axle (e.g., a spindle or a crankshaft), a first bearing assembly at or adjacent to the first end124of the bracket120, and a second bearing assembly at or adjacent to the second end128of the bracket120. The spindle extends through the bracket120and is held in position by the first bearing assembly and the second bearing assembly. The spindle functions as, for example, a torque transmission shaft. The spindle is longer than the bracket120such that the first arm122and the second arm126may be attached to the spindle outside of the bracket120. Due to the connection of the spindle to the first bearing assembly and the second bearing assembly, the spindle is able to rotate relative to the bracket and thus, the frame52of the bicycle50. In one embodiment, the crankset77does not include the bracket120, and the first bearing assembly and the second bearing assembly are attached directly to the frame52of the bicycle50.

The one or more sprockets F are attached to one of the first arm122and the second arm126(e.g., the second arm126). For example, the second arm126and the one or more sprockets F are attached to each other with, for example, one or more connectors. For example, the sprocket F1is disposed between the first arm122and the bracket120, and a connection of the first arm122to the spindle with, for example, a bolt and a threaded opening in the spindle presses the sprocket F1and the second arm126together. In one embodiment, the second arm126, for example, and the one or more sprockets F are formed as a single integral part.

The first arm122is connected to the spindle at and/or adjacent to a first end of the spindle (e.g., adjacent to the first end124of the bracket120), and the second arm126and the sprocket F1, for example, are connected to the spindle at and/or adjacent to a second end of the spindle (e.g., adjacent to the second end128of the bracket120). The second end of the spindle is opposite the first end of the spindle.

The first arm122and the second arm126may be connected to the spindle in any number of ways. For example, the spindle may be hollow and may be tapped at the first end and/or the second end of the spindle, respectively, and one or more bolts may be used to attach the first arm122and/or the second arm126to the spindle. Other connectors may be used to attach the first arm122and/or the second arm126to the spindle. For example, one or more cotters may be used to attach the first arm122and/or the second arm126to the spindle. Alternatively or additionally, the spindle may be any number of different shapes to facilitate positioning and attachment of the first arm122and/or the second arm126to the spindle. For example, the spindle may be a square tapered spindle, a hexagonal tapered spindle, a splined bottom bracket spindle, or another type of spindle. The first arm122and/or the second arm126may be attached to the spindle in other ways.

The first arm122and the second arm126each include an attachment portion130for attaching a pedal (not shown) to the crank set77. The attachment portions130are, for example, threaded openings via which the pedals are attached. Each of the pedals includes corresponding threading on a rod that interacts with a respective one of the attachment portions130to attach the respective pedal to the crank set77.

The crank set77may include additional, fewer, and/or different components. For example, the crank set77may include one or more spacers. The size and/or number of spacers may be set based on a width of the frame52of the bicycle50and/or a width of the bracket120, for example.

A power meter for a bicycle determines power output by a rider of the bicycle. A crank-based power meter includes, for example, a strain gauge that measures torque applied to a spindle (e.g., the spindle of the crank set77). For crank-based power meters of the prior art, the strain gauge is positioned on an outer surface of the spindle. Such positioning exposes the strain gauge to potential damage during installation and the environment during riding of the bicycle.

Referring toFIGS. 3-4, the spindle is part of an axle assembly132. The axle assembly132also includes a sensor assembly134. The sensor assembly134is, for example, a power meter, though other sensor assemblies may be provided.

As discussed below, the sensor assembly134includes a removable portion136(e.g., a sled) and a fixed portion (e.g., a fixed strain gauge assembly). The removable portion136is supported by the spindle at and/or adjacent to the first arm122. In another embodiment, the removable portion136is supported by the spindle at and/or adjacent to the second arm126. The removable portion136is removably attachable and electrically connectable to the fixed portion. At least part of the fixed portion of the sensor assembly is positionally fixed relative to the spindle and includes one or more sensors. The one or more sensors include at least one strain gauge. Other types of sensors may be provided.

The one or more sensors are disposed on one or more inner surfaces (e.g., an inner wall), respectively, of the spindle. This positioning protects the one or more sensors from damage during installation and protects the one or more sensors from the environment during riding of the bicycle.

Referring toFIG. 5, both the removable portion136and the fixed portion140of the sensor assembly134are supported by the spindle142. The spindle142has one or more inner walls144(e.g., an inner wall) extending along at least a portion of a length of the spindle142between a first end146and a second end148of the spindle142(e.g., between the first end146and a seal), and the inner wall144at least partially defines a first volume150and a second volume152within the spindle142. The first volume150is closer to the first end146of the spindle142than the second volume152is relative to the first end146of the spindle142. The first volume150has a first diameter D1, and the second volume152has a second diameter D2. The second diameter D2is greater than the first diameter D1, such that the inner wall144is a necked inner wall. The first diameter D1and the second diameter D2may be any number of sizes. For example, the first diameter D1may be 19 mm, and the second diameter D2may be approximately 24 mm. Other dimensions of the first diameter D1and the second diameter D2may be provided.

The inner wall144shown inFIG. 5is cylindrical with a varied sized circular cross-section along the length of the spindle142. In other embodiments, the one or more inner walls144form other cross-sectional shapes. For example, the one or more inner walls144may include at least four walls that form a rectangular cross-section along at least part of the length of the spindle142.

In the embodiment shown inFIG. 5, the fixed portion140of the sensor assembly134is disposed entirely within the second volume152within the spindle142, and at least part of the removable portion136of the sensor assembly134is disposed within the first volume150within the spindle142. In another embodiment, the removable portion136is disposed entirely within the first volume150within the spindle142, and at least part of the fixed portion140is disposed within the second volume152within the spindle142. In yet another embodiment, at least part of the removable portion136is disposed within the first volume150within the spindle142, and at least part of the fixed portion140is disposed within the second volume152within the spindle142. For example, the fixed portion140is disposed within both the second volume152and the first volume150within the spindle142. The removable portion136may also be disposed within both the second volume152and the first volume150within the spindle142.

The fixed portion140of the sensor assembly134includes one or more sensors153. For example, as shown in the embodiment ofFIG. 5, the fixed portion140of the sensor assembly may include two sensors (e.g., a first sensor153aand a second sensor153b). The fixed portion140may include more or fewer sensors153. The one or more sensors153may include any number of different types of sensors. For example, the first sensor153aand the second sensor153bmay be strain gauges. The one or more sensors153may include additional and/or different types of sensors.

The first sensor153aand the second sensor153bare disposed opposite each other on the inner wall144within the second volume152within the spindle142, such that the first sensor153aand the second sensor153bface each other. In the embodiment shown inFIG. 5, the first sensor153aand the second sensor153bare both disposed entirely within the second volume152within the spindle142. Other positioning of the first sensor153aand the second sensor153brelative to each other and relative to the spindle142may be provided.

The fixed portion140of the sensor assembly134is fixed in that at least part of the fixed portion140is positionally fixed relative to the spindle142. For example, at least the first sensor153aand the second sensor153bare positionally fixed relative to the spindle142. The first sensor153aand the second sensor153bare attached to (e.g., positionally fixed relative to) the spindle142with, for example, an adhesive (e.g., very high bond pressure sensitive adhesive (VHB PSA)).

The fixed portion140of the sensor assembly134includes any number of additional components. For example, as shown in the example ofFIG. 5, the fixed portion140of the sensor assembly134includes a circuit board154(e.g., a printed circuit board (PCB)). The circuit board154is supported by a body156(e.g., a housing of a radially expandable applicator) of the fixed portion140of the sensor assembly134.

The first sensor153aand the second sensor153b, for example, are attached and electrically connected to the PCB154in any number of ways including, for example, with flexible flat cables (FFCs)158. Wires or other electrical conductors may be provided to electrically connect and attach the two sensors153to the PCB154of the fixed portion140of the sensor assembly134. The FFCs158, for example, are attached and electrically connected to the two sensors153, respectively, and the PCB154via respective pads on the PCB154.

The fixed portion140of the sensor assembly134may include a number of components supported by the PCB154. For example, the fixed portion140of the sensor assembly134includes a controller160(e.g., a microcontroller) and one or more other electronic devices162(e.g., an analog-to-digital (A/D) converter or an amplifier) supported by the PCB154. The controller160may be configured for communication with the removable portion136. The A/D converter162may be configured to convert analog data generated by the two sensors153, for example, to a digital signal. Such conversion may be provided so that analog data is not transmitted from the fixed portion140of the sensor assembly134to the removable portion136of the sensor assembly134. For example, the A/D converter162may convert analog signals generated by the first sensor153aand the second sensor153binto digital signals, respectively. The fixed portion140of the sensor assembly134may transmit the digital signals to the removable portion136of the sensor assembly134when the removable portion136is electrically connected to the fixed portion140.

In one embodiment, the fixed portion140of the sensor assembly134does not include an A/D converter but includes an amplifier162. The amplifier amplifies the analog signals generated by the first sensor153aand the second sensor153, respectively. The fixed portion140of the sensor assembly134may transmit the amplified analog signals to the removable portion136of the sensor assembly134when the removable portion136is electrically connected to the fixed portion140.

The controller160and the A/D converter162are electrically connected to each other via tracks of the PCB154, and the controller160and the A/D converter162are electrically connected to the two sensors153via tracks and pads of the PCB154, and the FFCs158. The controller160and the A/D converter162may be supported by different sides of the PCB154, as shown inFIG. 5, or may be supported by a same side of the PCB154.

The fixed portion140of the sensor assembly134may include more, fewer, and/or different components. For example, the fixed portion140of the sensor assembly134also includes a memory. In one embodiment, the memory is part of the controller160and/or the A/D converter162, and the fixed portion140of the sensor assembly134does not include a separate memory. In another embodiment, the fixed portion140of the sensor assembly134does not include the controller160, and the A/D converter162is configured for communication with the removable portion136and for storing data.

The memory may store any number of different types of data for the sensor assembly134. For example, the memory may store calibration data that is specific to a particular sensor assembly134installed on a particular bicycle. In other words, memories of different sensor assemblies134installed on different bicycles store different calibration data.

As another example, as shown in the example ofFIG. 5, the fixed portion140of the sensor assembly134also includes a connector164, to which the removable portion136is attachable and electrically connectable. The connector164may be any number of different types of connectors including, for example, a USB connector (e.g., a female USB connector). Power and data may be transmitted from the removable portion136to the fixed portion140of the sensor assembly134via the USB connector164, for example, and data may be transmitted from the fixed portion140to the removable portion136of the sensor assembly134via the USB connector164. Other types of connectors may be provided.

The removable portion136of the sensor assembly134is electrically connectable and physically attachable to the fixed portion140of the sensor assembly134via, for example, the connector164. The removable portion136of the sensor assembly134includes a connector166that corresponds to the connector164of the fixed portion140of the sensor assembly134. For example, the removable portion136includes a USB connector166(e.g., a male USB connector) that corresponds to the USB connector164of the fixed portion140of the sensor assembly134. The USB connector166of the removable portion136of the sensor assembly134includes one or more electrical conductors167(e.g., seeFIG. 7; a first pin for power, a second pin for GND, a third pin for RX, and a fourth pin for TX; serial communication with only the third pin for RX and the fourth pin for TX being used for communication with the USB connector164of the fixed portion140of the sensor assembly134) via which the removable portion136of the sensor assembly134is electrically connectable to the fixed portion140of the sensor assembly134. In one embodiment, standard asynchronous serial communication is used between the USB connector164of the fixed portion140and the USB connector166of the removable portion136of the sensor assembly134, as standard asynchronous serial communication has a high enough data rate for this application and a low overhead.

Referring toFIGS. 5-6, the removable portion136of the sensor assembly134includes a housing168that supports a circuit board170(e.g., a PCB). The housing168includes a main portion168aand a removable door168bthat is attached (e.g., press fit or with one or more connectors) to the main portion168a. The removable door168bof the housing168includes an opening171through which the circuit board170and/or the USB connector166of the removable portion136of the sensor assembly134extends. Components of the removable portion136of the sensor assembly134(e.g., a power source172) are accessible via the removable door168b. In the embodiment shown inFIGS. 5-6, the removable door168bof the housing168also includes a seal173(e.g., a rubber O-ring) that, for example, helps protect components disposed within the main portion168aof the housing168from moisture and debris.

The PCB170of the removable portion136of the sensor assembly134supports and electrically connects any number of components. For example, the PCB170supports and electrically connects the power source172to the USB connector166(e.g., via tracks of the PCB170). The power source172may be any number of different types of power sources including, for example, a battery (e.g., a lithium ion battery).

When the removable portion136of the sensor assembly134is electrically connected to the fixed portion140of the sensor assembly134via the USB connectors164,166, the battery172, for example, is electrically connected to components of the fixed portion140of the sensor assembly134. For example, the battery172may power the two sensors153, the controller160, and/or the A/D converter162via the PCB170and the USB connector166of the removable portion136of the sensor assembly134, and the USB connector164and the PCB154of the fixed portion140of the sensor assembly134.

When the removable portion136of the sensor assembly134is disconnected from the fixed portion140of the sensor assembly134(e.g., the USB connector166of the removable portion136is removed from the USB connector164of the fixed portion140) and removed from the bicycle50, the battery172may be recharged via, for example, the USB connector166of the removable portion136. For example, the USB connector166of the removable portion136may be plugged into a USB power adapter, and the USB power adapter may be plugged into a wall outlet. In one embodiment, the battery172is not rechargeable but is user replaceable.

The battery172, for example, may be electrically connected and attached to the PCB170of the removable portion136of the sensor assembly134in any number of ways. For example, the removable portion136of the sensor assembly134may include a battery holder, in which the battery172is positionable, and pins and/or wires of the battery holder may be attached and electrically connected (e.g., soldered) to corresponding pads on the PCB170of the removable portion136of the sensor assembly134. Other configurations may be provided.

The removable portion136of the sensor assembly134may include more and/or different components. For example, the removable portion136of the sensor assembly134may include an antenna174and/or a Bluetooth and ANT+ radio configured to communicate with other components on the bicycle50(e.g., the control device100) and/or one or more computing devices outside of the bicycle50.

In one embodiment, the antenna174is positioned on the PCB170of the removable portion136of the sensor assembly134opposite an outer end surface175of the removable portion136, such that the antenna174is disposed outside of the spindle142when the removable portion136of the sensor assembly134is installed (e.g., attached to the fixed portion140of the sensor assembly134). In another embodiment, the antenna174is within the spindle142but adjacent to the first end146of the spindle142when the removable portion136of the sensor assembly134is installed. The spindle142may act as a shield as to communications to and/or from the antenna174. The positioning of the antenna174outside of the spindle142and/or adjacent to the first end146of the spindle142may thus provide for better communicating using the antenna174compared to other positioning of the antenna174within the spindle142.

The removable portion136of the sensor assembly134may include other components. For example, the removable portion136of the sensor assembly134may include a controller176(e.g., a microcontroller), a memory178, and a light-emitting diode (LED)180(seeFIGS. 7-8). In one embodiment, the removable portion136includes additional, fewer, and/or different components. For example, the removable portion136of the sensor assembly134may include a voltage controller (e.g., to control current to power components of the fixed portion140of the sensor assembly134), a voltage converter, a charge controller (e.g., to control charging current), one or more accelerometers, a button, and/or other components. In one embodiment, when the removable portion136of the sensor assembly134is electrically connected to the fixed portion140of the sensor assembly134, current flows from the battery172, via the voltage converter, through the USB connectors164,166to power the fixed portion140of the sensor assembly134.

The controller176of the removable portion136may process data received from outside of the sensor assembly134and/or data received from the fixed portion140of the sensor assembly134. For example, the controller176may receive digital data representing forces measured by the two sensors153from the fixed portion140of the sensor assembly134, and may calculate a power output based on the measured forces and a measured cadence (e.g., measured by one or more sensors at the first arm122and/or the second arm126). The controller176may receive the measured cadence via, for example, the antenna174. The calculated power may represent power for only one of the legs (e.g., the left leg). The controller176may also estimate a total power (e.g., for the left leg and the right leg) based on the calculated power.

The memory178may store any number of types of data. For example, the memory178may store historical values of the measured forces and/or the measured cadence, and/or may store historical values of the calculated power output. The memory178may store additional and/or different data.

Referring toFIGS. 7-8, the housing168of the removable portion136of the sensor assembly134includes a window184, and the LED180provides feedback to the rider of the bicycle50, for example, via the window184. The window184is, for example, a portion of the housing168that is made of transparent material.

The controller176, for example, may be configured to turn on the LED180when the sensor assembly134is in any number of states. For example, the controller176may turn the LED180on and red when a charge level of the battery172is below a predetermined charge level. Further, the controller176may turn the LED180on and green when the charge level of the battery172is above the predetermined charge level, when the battery172is charging, and/or when the removable portion136of the sensor assembly134is electrically connected to the fixed portion140of the sensor assembly134. Other feedback from the LED180may be provided.

Referring toFIGS. 5-6, the battery172, the antenna174, the controller176, the memory178, and the LED180, for example, are electrically connected to each other via tracks of the PCB170. The battery172, and the antenna174, the controller176, the memory178, and the LED180may be supported by different sides of the PCB170, as shown inFIG. 5, or may be supported by a same side of the PCB170. The battery172, the antenna174, the controller176, the memory178, and the LED180, for example, are electrically connected to the USB connector166via tracks and/or one or more pads of the PCB170.

Again referring toFIG. 5, the inner wall144may define additional volumes within the spindle142. For example, the inner wall144may at least partially define a third volume186and a fourth volume188. The third volume186is adjacent to the second volume152, and the third volume186is separated from the second volume152by a radially-inward extending flange190(e.g., a flange). The third volume186may be any number of sizes and/or shapes. For example, the third volume186may be cylindrically-shaped and may have a third diameter D3that is a same size as the second diameter D2. Other sizes and/or shapes may be provided.

In one embodiment, the third volume186within the spindle142is filled with a filler192. Any number of different types of fillers192including, for example, an epoxy may be provided in the third volume186. The filler192, with the removable portion136of the sensor assembly134, when installed, protects the second volume152, and thus, the sensors153of the fixed portion140of the sensor assembly134, from the environment in which the axle assembly132is being used. For example, the filler192within the third volume186and the removable portion136of the sensor assembly134, when installed, prevent water and debris from getting into the second volume152within the spindle142. In the embodiment shown inFIG. 5, the axle assembly132also includes a seal194positioned on the flange190. The seal194may be made of any number of materials including, for example, rubber, and fills an opening between the second volume152and the third volume186within the spindle142. The seal194further protects the second volume152, and thus, the sensors153of the fixed portion140of the sensor assembly134, from the environment in which the axle assembly132is being used. In one embodiment, the axle assembly132does not include the seal and/or the filler192.

The fourth volume188is adjacent to the third volume186and the second end148of the spindle142. The fourth volume188may be any number of sizes and/or shapes. For example, the fourth volume188may be cylindrically-shaped and may have a fourth diameter D4that is a same size as the first diameter D1. Other sizes and/or shapes may be provided.

In the embodiment shown inFIG. 5, the inner wall144is threaded within at least part of the fourth volume188. The second arm126is attached to the second end148of the spindle142with a connector196via the threaded part of the fourth volume188within the spindle142. The connector196may be any number of different types of connectors including, for example, a bolt. The sprocket F1is disposed between the second bearing assembly198and the second arm126. The second bearing assembly198presses the sprocket F1against the second arm126when the second arm126is attached to the spindle142via the bolt196and the threaded part of the fourth volume188within the spindle142.

The first end146of the spindle142includes a flange200that extends around a circumference of the spindle142. The flange200of the spindle142is positioned within a corresponding channel202at an outer surface204of the first arm122, such that the first arm122stays on the spindle142. The first arm122includes a threaded portion206, to which a spacer208may be attached. A part210of the spacer208is disposed between the first arm122and the first bearing assembly212. In one embodiment, the spacer208is a bearing assembly preload adjuster that adjusts bearing preload for the first bearing assembly212and the second bearing assembly198, and reduces or removes side-to-side play of the first arm122relative to the spindle142.

The axle assembly132includes a number of features that facilitate positioning of the sensor assembly134within the spindle142. Referring toFIG. 5, the axle assembly132includes protrusions220(e.g., flanges, ribs, retaining elements) extending from one or more outer surfaces of the removable portion136of the sensor assembly134(e.g., extending from the main portion168aof the housing168of the removable portion136), a base222that interacts with the fixed portion140of the sensor assembly134, and a guide224that interacts with the fixed portion140of the sensor assembly134and/or the base222.

The flanges220extending from the removable portion136of the sensor assembly134facilitate insertion into and positioning relative to the spindle142. For example, in one embodiment (seeFIGS. 6, 7, and 9), the removable portion136of the sensor assembly134includes one or more outer surfaces226(e.g., two opposite flat surfaces or a circumferential surface) that are disposable within the spindle142when the removable portion136is installed in the axel assembly132. The flanges220are spaced apart from each other along the one or more outer surfaces226and extend along or around the one or more outer surface226.

The flanges220are sized such that the flanges220abut the inner wall144of the spindle142when the removable portion136is installed. For example, a first flange220aand a second flange220bare sized (e.g., have a height) to abut the inner wall144within the first volume150within the spindle142when the removable portion136is installed. A third flange220cand a fourth flange220deach have a greater height than a height of the first flange220aand the second flange220b, such that the third flange220cand the fourth flange220dabut the inner wall144of the spindle142within a fifth volume228within the spindle142that is adjacent to the first end146of the spindle142. More or fewer flanges may be provided on the removable portion136of the sensor assembly134to facilitate insertion and positioning of the removable portion136of the sensor assembly134relative to the spindle142.

In one embodiment, the flanges220are made of a compliant material (e.g., rubber). In another embodiment, the flanges220are rigid and made of a same material as the rest of the main portion168aof the housing168of the removable portion136of the sensor assembly134.

The base222is attached to the inner wall144of the spindle142, and at least part of the base222is disposed within the second volume152of the spindle142. The base222may be attached to the inner wall144of the spindle142in any number of ways including, for example, with an adhesive (e.g., a VHB PSA). In the embodiment shown, the base222is formed by two separate base parts222a,222b(e.g., base insets) that are disposed opposite each other on the inner wall144within the second volume152of the spindle142.

In one embodiment, prior to attachment to the spindle142, the two separate base parts222a,222bare attached to an expandable installation tool. The expandable installation tool, with the two separate base parts222a,222battached, fits through the first volume150within the spindle142and into the second volume152within the spindle142. In other words, a maximum diameter of the expandable installation tool, with the two separate base parts222a,222battached, is smaller than the first diameter D1of the first volume150within the spindle142.

The installation tool is expanded, such that the two separate base parts222a,222bare pressed against and adhered to the inner wall144within, for example, the second volume152within the spindle142. The installation tool is collapsed and removed from the spindle142. The expandable installation tool locates and clocks the two separate base parts222a,222b. In other words, the expandable installation tool is configured to fit on and in the spindle142such that the two separate base parts222a,222bare installed on the inner wall144of the spindle142in predetermined positions (e.g., circumferentially relative to the inner wall144of the spindle142and at particular distances into the second volume152within the spindle142), respectively.

Referring toFIG. 10, the fixed portion140of the sensor assembly134includes a radially expandable applicator229that is formed by a body230, retaining elements232supported by the body230, and wings234(e.g., two wings) supported by the body230. In one embodiment, the radially expandable applicator229(e.g., the body230, the retaining elements232, and the wings234) is formed as a single molded part. In another embodiment, one or more of the body230, the retaining elements232, the wings234are separate parts attached to the rest of the fixed portion140of the sensor assembly134.

Referring toFIG. 5, the retaining elements232are sized and shaped to fit into (e.g., clip or snap into) corresponding recesses within the two separate base parts222a,222b, respectively. When the retaining elements232of the fixed portion140of the sensor assembly134are snapped into the two separate base parts222a,222b, respectively, at least part of the fixed portion140of the sensor assembly134is positionally fixed and clocked relative to the inner wall144of the spindle142.

Referring again toFIG. 10, the wings234are expandable and retractable. For example, the wings234are attached to the body230via active hinges236that allow the wings234to move away from each other and/or towards each other. Each of the wings234supports a respective strain gauge153. For example, a first of the wings234asupports the first strain gauge153a, and a second of the wings234bsupports the second strain gauge153b.

In one embodiment, the first strain gauge153aand the second strain gauge153bare attached to the first wing234aand the second wing234bvia a first layer of material238a(e.g., a first pad) and a second layer of material238b(e.g., a second pad), respectively. Referring toFIGS. 5 and 10, one side of the first pad238ais attached to the first wing234awith an adhesive, and the first strain gauge153ais attached to another, opposite side of the first pad238awith the adhesive or another adhesive. One side of the second pad238bis attached to the second wing234bwith an adhesive, and the second strain gauge153bis attached to another, opposite side of the second pad238bwith the adhesive or another adhesive.

The first pad238aand the second pad238bmay be made of any number of materials. For example, the first pad238aand the second pad238bmay be made of silicone, rubber, or silicone rubber. Other materials may be used.

The first pad238aand the second pad238bmay be any number of sizes (e.g., thicknesses). Even pressure on the strain gauges153while the first pad238aand the second pad238bare adhered to the inner wall144of the spindle142increases the chances of successful bonding. A bonding pressure may be varied by varying a compression on the first pad238aand the second pad238b. The compression may be varied by changing the thickness of the first pad238aand the second pad238b. In other words, the thickness of the first pad238aand the second pad238bmay be set based on the bonding pressure to be provided for adhering the first pad238aand the second pad238bto the inner wall144of the spindle142. A hardness of the first pad238aand the second pad238bmay also be set (e.g., the material of the first pad238aand the second pad238bmay be chosen) based on the bonding pressure to be provided.

Referring toFIGS. 5 and 10, the fixed portion140of the sensor assembly134may include fasteners240(e.g., clips) that further attach the strain gauges153to the wings234, respectively. The clips240locate and support the strain gauges153, respectively. During installation of the fixed portion140of the sensor assembly134(e.g., the attachment of the strain gauges153to the inner wall144of the spindle142), the clips240push out of the way and form part of a flexible circuit between the strain gauges153and the PCB154of the fixed portion140of the sensor assembly134.

FIGS. 11-13illustrate an exemplary installation process for the fixed portion140of the sensor assembly134. As shown inFIG. 11, after the two separate base parts222a,222bhave been installed (e.g., adhered to the inner wall144of the spindle142), the fixed portion140of the sensor assembly134is moved into the spindle142. The radially expandable applicator229is in a first configuration. The first configuration of the radially expandable applicator229is a closed configuration that allows the fixed portion140of the sensor assembly134to move through the first volume150within the spindle142. In one embodiment, the radially expandable applicator229is kept in the closed configuration (seeFIGS. 10-12) with one or more fasteners242(e.g., two fasteners; two sets of snaps or clasps on opposite sides of the radially expandable applicator229). The two fasteners242, for example, keep the wings234folded in while the fixed portion140of the sensor assembly134is moved through the spindle142(e.g., through the first volume150within the spindle142).

A tool (not shown) may be used to move the fixed portion140of the sensor assembly134through a portion of the spindle142(e.g., through the first volume150within the spindle142and part of the second volume152within the spindle142). The tool interacts with a force applicator246(e.g., a pusher) positioned within and/or against the fixed portion140of the sensor assembly134(e.g., within the radially expandable applicator229) to move the pusher246, and thus the fixed portion140of the sensor assembly134, through part of the spindle142. The pusher246may be any number of shapes (e.g., cylindrical) and sizes. For example, the pusher246may be sized based on the bonding pressure to be provided. The pusher246remains within the spindle142after the fixed portion140of the sensor assembly134is installed.

Referring toFIG. 12, the tool and the pusher246are used to move the fixed portion140of the sensor assembly134into contact with and attachment to the base parts222a,222bvia, for example, the retaining elements232of the radially expandable applicator229.

Referring toFIG. 13, once the retaining elements232of the radially expandable applicator229of the fixed portion140of the sensor assembly134are attached to the base parts222a,222b, the tool is then used to move the pusher246further into the spindle142, and thus the radially expandable applicator229. This movement applies pressure to the wings234of the radially expandable applicator229until the two fasteners242release, and the wings234move radially outward towards the inner wall144of the spindle142. Each of the strain gauges153includes a layer of adhesive disposed on an exposed surface (e.g., a surface facing the inner wall144) of the respective strain gauge153, such that as the pusher246moves further into the radially expandable applicator229, the wings234hinge towards the inner wall144of the spindle142until the strain gauges153are connected to the inner wall144of the spindle142via the layers of adhesive disposed on the exposed surfaces of the strain gauges153, respectively.

FIG. 13illustrates a second configuration of the radially expandable applicator229. The second configuration of the radially expandable applicator229is an open configuration in which the strain gauges153are connected to the inner wall144of the spindle142via the layers of adhesive, respectively.FIG. 13also illustrates a final position of the pusher246within the radially expandable applicator229once installation of the fixed portion140of the sensor assembly134is complete. In this position, the pusher246and the wings234press the strain gauges153to the inner wall144of the spindle142until the adhesive between the strain gauges153and the inner wall144of the spindle142cures.

The guide224is then attached to one or more of the two separate base parts222a,222band/or the radially expandable applicator229. For example, the guide may be sized and shaped to be press fit onto the two separate base parts222a,222band/or the radially expandable applicator229. An inner portion of the guide224may be triangularly-shaped to guide, for example, the USB connector166of the removable portion136of the sensor assembly134towards the USB connector164of the fixed portion140of the sensor assembly134, and thus, electrically connect and physically attach the removable portion136to the fixed portion140of the sensor assembly134. Other configurations of the guide224may be provided. In one embodiment, the axle assembly132does not include the guide224.

Once the fixed portion140of the sensor assembly134is installed within the spindle142of the axle assembly132, the removable portion136of the sensor assembly134may be physically and electrically connected to the fixed portion140. The battery172, for example, then powers the strain gauges153, which measure forces on the spindle142(e.g., generate analog data that represents the forces on the spindle142). The fixed portion140of the sensor assembly134converts the generated analog data into digital data and transmits the digital data, which represents the measured forces, to the removable portion136of the sensor assembly134. The removable portion136of the sensor assembly134calculates a power output by a rider based on the digital data received at the removable portion136. The removable portion136of the sensor assembly134transmits the calculated power output to one or more other components of the bicycle50(e.g., the control device) and/or outside of the bicycle50(e.g., a mobile device).

The attachment of the strain gauges153to the inner wall144of the spindle142protects the strain gauges153from the environment in which the bicycle50is being ridden, and protects the strain gauges153from damage during installation of the crank assembly77on the bicycle50. Further, by mounting the strain gauges153inside the spindle142, the spindle142does not require a hole through which gauge signal and power wires are passed.