Patent Description:
Electric-assisted bicycles, whose use is on the rise worldwide in recent years, come with electric-assisted motors and batteries. The electric-assisted bicycles enable cyclists to ride along steep or rugged roads easily and effortlessly, as the cyclists can exert a pedal force of variable magnitude on foot pedals to cause the electric-assisted motors to generate considerable auxiliary power.

The magnitude of the pedal force is conventionally sensed with a torque sensing assembly disposed outside the bushing of the bearing of the crankshaft of the electric-assisted bicycle to sense any variations in the torque to determine whether to start the motor. However, many cyclists complain that they are denied access to appropriate auxiliary power while riding electric-assisted bicycles whenever a variation in the pedal force falls outside the sensitivity or sensing range of the torque sensing assembly. TWI769802 discloses a pedal force detection mechanism for an electric-assisted bicycle according to the preamble of claim <NUM>.

In view of the aforesaid drawbacks of the prior art, it is an objective of the present disclosure to provide a pedal force detection mechanism for an electric-assisted bicycle to sufficiently respond to a variation in pedal force with a view to efficiently and accurately supplying auxiliary power.

To achieve the above and other objectives, the present disclosure provides a pedal force detection mechanism for an electric-assisted bicycle, adapted to be received in a shaft housing of the electric-assisted bicycle to coordinate with a crankshaft and connect to an auxiliary power assembly. The crankshaft is movably disposed at the shaft housing. The pedal force detection mechanism comprises a pedal force diverting portion for transmitting a pedal force of the crankshaft unidirectionally and diverting the pedal force along an axial direction of the crankshaft, a main thrust bearing for abutting against the pedal force diverting portion to transmit the diverted pedal force, a strain sensing assembly having a strain gauge, a resilient ring-shaped base and a supporting annular base, with the supporting annular base disposed outside of the torque-transmitting member and abutting against the shaft housing, allowing an axial-strain gap to be defined between the supporting annular base and the main thrust bearing, the resilient ring-shaped base being disposed outside the supporting annular base and fitted between the main thrust bearing and the supporting annular base, the strain gauge being disposed at the resilient ring-shaped base and in signal connection with the auxiliary power assembly; and a main drive gear movably disposed between the crankshaft and the shaft housing and having a main gear, an internally-connected ring body and an externally-connected ring body, the internally-connected ring body being integrally formed with the main gear and located on an inner side of the main gear, the externally-connected ring body being fixedly connected to an outer side of the main gear, wherein the torque-transmitting member and the internally-connected ring body rotate synchronously, and an axial-movement gap is defined between the torque-transmitting member and the internally-connected ring body.

In an embodiment, the main thrust bearing is a ball thrust bearing.

In an embodiment, the supporting annular base has a supporting cylindrical body and a supporting annular flange, with the axial-strain gap defined between a side of the supporting cylindrical body and the main thrust bearing, and another side of the supporting cylindrical body is fixedly connected to the supporting annular flange, allowing the supporting annular flange to be fitted between the resilient ring-shaped base and the shaft housing.

In an embodiment, the main drive gear has a first thrust bearing, a second thrust bearing, an adjustment nut, and a fixation nut, with the first thrust bearing fitted between the shaft housing and the main gear, the second thrust bearing fitted between the main gear and the adjustment nut, the adjustment nut is fastened to the crankshaft, and the fixation nut fastened to the crankshaft and abutting against the adjustment nut, allowing a fastening direction of the fixation nut to be opposite to a fastening direction of the adjustment nut.

In an embodiment, the pedal force detection mechanism further comprises a rotation sensor unit, and the rotation sensor unit has a sensor, a annular magnet, an annular gripping component, a third thrust bearing and a first shaft bearing, the annular gripping component being fixedly fitted to the crankshaft, the third thrust bearing being fitted between the annular gripping component and the torque-transmitting member, the first shaft bearing being disposed between the shaft housing and the annular gripping component, the annular magnet being disposed at the annular gripping component, and the sensor being disposed at the shaft housing to sense the annular magnet.

Therefore, according to the disclosure, the pedal force detection mechanism for an electric-assisted bicycle sufficiently responds to a variation in a treading force with a view to supplying auxiliary power.

To facilitate understanding of the object, characteristics, and effects of the present disclosure, embodiments together with the attached drawings for the detailed description of the present disclosure are provided.

Referring to <FIG>, the disclosure provides a pedal force detection mechanism for an electric-assisted bicycle. The pedal force detection mechanism is adapted to be received in a shaft housing <NUM> of the electric-assisted bicycle to coordinate with a crankshaft <NUM> and connect to an auxiliary power assembly <NUM>. The crankshaft <NUM> is movably disposed at the shaft housing <NUM>. The shaft housing <NUM> comprises a combination of a first shaft housing <NUM> and a second shaft housing <NUM>. The first shaft housing <NUM> comprises a positioning chamber <NUM> and an annular cover <NUM>. The annular cover <NUM> covers the positioning chamber <NUM>. The crankshaft <NUM> is penetratingly disposed at the annular cover <NUM> and the positioning chamber <NUM> of the first shaft housing <NUM> and the second shaft housing <NUM>. Alternatively, the shaft housing <NUM> is a shaft housing of any other structure. The auxiliary power assembly <NUM> comprises a combination of an auxiliary power source <NUM>, a first deceleration gear <NUM>, and a second deceleration gear <NUM>. Alternatively, the auxiliary power assembly <NUM> is an auxiliary power mechanism of any other type. The pedal force detection mechanism comprises a torque-transmitting member <NUM>, a main thrust bearing <NUM>, a strain sensing assembly <NUM>, and a main drive gear <NUM>. The torque-transmitting member <NUM> transmits a torque F of the crankshaft <NUM> unidirectionally and diverts the torque F along the axial direction of the crankshaft <NUM>. The torque-transmitting member <NUM> comprises a combination of a single-directional roller clutch <NUM>, an active end-face cam <NUM> and a passive end-face cam <NUM> to transmit the torque F of the crankshaft <NUM> unidirectionally and divert the torque F along the axial direction of the crankshaft <NUM>. A shaft-supporting member <NUM> is disposed between the active end-face cam <NUM> and the positioning chamber <NUM> of the first shaft housing <NUM>. Alternatively, the torque-transmitting member <NUM> is a treading force diverting mechanism of any other type. The main thrust bearing <NUM> abuts against the torque-transmitting member <NUM> to transmit the torque F diverted. The main thrust bearing <NUM> abuts against a backing plate <NUM> of the passive end-face cam <NUM> of the torque-transmitting member <NUM> or abuts against a torque-transmitting member of any other type to transmit the torque F diverted. The strain sensing assembly <NUM> has a strain gauge <NUM>, a resilient ring-shaped base <NUM> and a supporting annular base <NUM>. The supporting annular base <NUM> is made of, for example, steel, disposed outside the passive end-face cam <NUM> of the torque-transmitting member <NUM>, and adapted to abut against the bottom of the positioning chamber <NUM> of the shaft housing <NUM>. An axial-strain gap <NUM> is defined between the supporting annular base <NUM> and the main thrust bearing <NUM>. The resilient ring-shaped base <NUM> is made of, for example, aluminum and disposed outside the supporting annular base <NUM>. An annular top surface <NUM> and an annular bottom surface <NUM> of the resilient ring-shaped base <NUM> abut against the main thrust bearing <NUM> and the supporting annular base <NUM> respectively, allowing the resilient ring-shaped base <NUM> to be fitted between the main thrust bearing <NUM> and the supporting annular base <NUM>. The strain gauge <NUM> is disposed on the outer circumferential surface of the resilient ring-shaped base <NUM> and is in signal connection with the auxiliary power assembly <NUM>. The strain gauge <NUM> is connected to a control circuit of the auxiliary power assembly <NUM> by wireless (for example, RFID, infrared, or radio communication) or wired connection. The main drive gear <NUM> is movably disposed between the crankshaft <NUM> and the shaft housing <NUM> and movably disposed between the positioning chamber <NUM> of the first shaft housing <NUM> and the second shaft housing <NUM>. The crankshaft <NUM> is penetratingly disposed at the main drive gear <NUM>. The main drive gear <NUM> has a main gear <NUM>, an internally-connected ring body <NUM> and an externally-connected ring body <NUM>. The internally-connected ring body <NUM> and the main gear <NUM> are integrally formed with each other, with the internally-connected ring body <NUM> located on the inner side of the main gear <NUM>. An inner shaft bearing <NUM> is disposed between the crankshaft <NUM>, the internally-connected ring body <NUM> and the main gear <NUM>. The externally-connected ring body <NUM> is fixedly connected to the outer side of the main gear <NUM>. An outer shaft bearing <NUM> is disposed between the externally-connected ring body <NUM> and the second shaft housing <NUM> and penetratingly disposed at the second shaft housing <NUM>. An axial spline <NUM> of the externally-connected ring body <NUM> is connected to a chassis (not shown). An axial spline <NUM> disposed outside the end of the passive end-face cam <NUM> of the torque-transmitting member <NUM> is movably connected to an axial spline <NUM> disposed inside the end of the internally-connected ring body <NUM>. Thus, the passive end-face cam <NUM> of the torque-transmitting member <NUM> and the internally-connected ring body <NUM> rotate synchronously. An axial-movement gap <NUM> is defined between the passive end-face cam <NUM> of the torque-transmitting member <NUM> and the internally-connected ring body <NUM>. The width of the axial-movement gap <NUM> is greater than or equal to the width of the axial-strain gap <NUM>. The supporting annular base <NUM> is disposed outside the junction of the passive end-face cam <NUM> and the internally-connected ring body <NUM>. The internally-connected ring body <NUM> is penetratingly disposed at the bottom of the positioning chamber <NUM> of the first shaft housing <NUM> so as to be movably connected to the passive end-face cam <NUM>.

As described above, according to the present disclosure, when the crankshaft <NUM> of the pedal force detection mechanism for an electric-assisted bicycle receives the torque F exerted by the cyclist and transmitted through foot pedals (not shown) and a crank (not shown), the crankshaft <NUM> drives the active end-face cam <NUM> through the single-directional roller clutch <NUM> to rotate unidirectionally to transmit the torque F, and then the active end-face cam <NUM> drives the passive end-face cam <NUM> to rotate and push the passive end-face cam <NUM> toward the crankshaft <NUM> to undergo axial movement. Thus, the torque F diverts along the axial direction of the crankshaft <NUM>. The passive end-face cam <NUM> undergoing axial movement toward the crankshaft <NUM> pushes the main thrust bearing <NUM>, and then the main thrust bearing <NUM> pushes the annular top surface <NUM> of the resilient ring-shaped base <NUM>. Since the annular bottom surface <NUM> of the resilient ring-shaped base <NUM> is blocked by the back of the supporting annular base <NUM> and the bottom of the positioning chamber <NUM> of the shaft housing <NUM>, the resilient ring-shaped base <NUM> deforms. After that, a piezoelectric material in the strain gauge <NUM> generates strain and undergoes voltage variation because of the deformation of the resilient ring-shaped base <NUM>. Next, torque is calculated according to the voltage variation. Then, the strain gauge <NUM> senses a torque generated under the torque F. If the torque generated under the torque F is greater than or equal to a predetermined torque, the auxiliary power source <NUM> will output auxiliary power to the main gear <NUM> through the first deceleration gear <NUM> and the second deceleration gear <NUM> to assist the cyclists in riding bicycles easily and effortlessly.

As described above, upon deformation of the resilient ring-shaped base <NUM>, the axial-strain gap <NUM> defined between the front of the supporting annular base <NUM> and the main thrust bearing <NUM> causes the supporting annular base <NUM> to underpin the main thrust bearing <NUM> immediately before the deformation of the resilient ring-shaped base <NUM> outstrips the axial-strain gap <NUM>, preventing the resilient ring-shaped base <NUM> from undergoing permanent deformation which might otherwise occur whenever the main thrust bearing <NUM> causes the resilient ring-shaped base <NUM> to deform excessively. With the axial-movement gap <NUM> being defined between the passive end-face cam <NUM> of the torque-transmitting member <NUM> and the internally-connected ring body <NUM> and greater than or equal to the axial-strain gap <NUM>, the active end-face cam <NUM> pushes the passive end-face cam <NUM> to move in the axial direction of the crankshaft <NUM>. Therefore the passive end-face cam <NUM> undergoes axial movement freely to enable the resilient ring-shaped base <NUM> to correctly deformation, allowing the strain gauge <NUM> to correctly sense the torque generated under the torque F. With the internally-connected ring body <NUM> being integrally formed with the main gear <NUM> and located on the inner side of the main gear <NUM>. An assembly process entails connecting movably the internally-connected ring body <NUM> to the passive end-face cam <NUM> of the torque-transmitting member <NUM> to not only enhance the ease of assembly but also reduce the processing process of the main drive gear <NUM>. Referring to <FIG>, the pedal force detection mechanism of the disclosure precisely senses and determines whether a pedal force has been inputted and thus has higher resolution than conventional pedal force detection mechanisms. Furthermore, the pedal force detection mechanism of the present disclosure can sense a pedal force of a great magnitude and thus has a larger sensing range than conventional pedal force detection mechanisms.

Referring to <FIG>, in an embodiment illustrated by the diagram, the main thrust bearing <NUM> is a ball thrust bearing. Therefore, the main thrust bearing <NUM> of the disclosure exhibits enhanced mechanical strength and durability.

Referring to <FIG> and <FIG>, in an embodiment illustrated by the diagrams, the supporting annular base <NUM> has a supporting cylindrical body <NUM> and a supporting annular flange <NUM>. The axial-strain gap <NUM> is defined between the front of the supporting cylindrical body <NUM> and the main thrust bearing <NUM>. The back of the supporting cylindrical body <NUM> is fixedly connected to the supporting annular flange <NUM>. The supporting annular flange <NUM> is fitted between the annular bottom surface <NUM> of the resilient ring-shaped base <NUM> and the bottom of the positioning chamber <NUM> of the shaft housing <NUM>. Therefore, the supporting annular base <NUM> of the disclosure exhibits enhanced mechanical strength and durability.

Referring to <FIG>, <FIG>, <FIG> and <FIG>, in an embodiment illustrated by the diagrams, the main drive gear <NUM> has a first thrust bearing <NUM> (for example, a needle roller thrust bearing), a second thrust bearing <NUM> (for example, a ball thrust bearing), an adjustment nut <NUM>, and a fixation nut <NUM>. The first thrust bearing <NUM> is fitted between the bottom of the positioning chamber <NUM> of the shaft housing <NUM> and the main gear <NUM>. The first thrust bearing <NUM> is fitted around the internally-connected ring body <NUM>. The second thrust bearing <NUM> is fitted between the main gear <NUM> and the adjustment nut <NUM>. The second thrust bearing <NUM> is fitted around the crankshaft <NUM> and disposed in the externally-connected ring body <NUM>. The adjustment nut <NUM> is fastened to the crankshaft <NUM> and disposed in the externally-connected ring body <NUM>. The fixation nut <NUM> is fastened to the crankshaft <NUM> and abuts against the adjustment nut <NUM>. The fixation nut <NUM> is disposed in the externally-connected ring body <NUM>. The fastening direction of the fixation nut <NUM> is opposite to the fastening direction of the adjustment nut <NUM>. As described above, according to the present disclosure, the assembly of the pedal force detection mechanism comprises the steps as follows: the adjustment nut <NUM> is rotated until it is fitted between the crankshaft <NUM> and the externally-connected ring body <NUM>; when the strain gauge <NUM> senses a signal (i.e., at the sensing starting point of the strain gauge <NUM>), the fixation nut <NUM> is rotated until it is fitted between the crankshaft <NUM> and the externally-connected ring body <NUM> to fasten the adjustment nut <NUM> in place. Therefore, the pedal force detection mechanism of the present disclosure is not only easy to assemble but also thereafter effective in confirming whether the strain gauge <NUM> is functioning well.

Referring to <FIG>, <FIG>, <FIG>, <FIG>, in an embodiment illustrated by the diagrams, the pedal force detection mechanism of the present disclosure further comprises a rotation sensor unit <NUM>. The rotation sensor unit <NUM> comprises a sensor <NUM> (for example, an electromagnetic sensor), an annular magnet <NUM> (for example, a Hall sensing magnet), an annular gripping component <NUM>, a third thrust bearing <NUM> (for example, a needle roller thrust bearing) and a first shaft bearing <NUM>. The annular gripping component <NUM> has a fixing hole <NUM> fixedly fitted to the crankshaft <NUM>. The third thrust bearing <NUM> is fitted between the back of the annular gripping component <NUM> and the active end-face cam <NUM> of the torque-transmitting member <NUM>. The first shaft bearing <NUM> is disposed at the annular cover <NUM> of the shaft housing <NUM> and fitted to the front of the annular gripping component <NUM>. The annular magnet <NUM> is disposed in an annular fixing groove <NUM> at the front of the annular gripping component <NUM>. The sensor <NUM> is disposed at the annular cover <NUM> of the shaft housing <NUM> to sense the annular magnet <NUM>. Therefore, the pedal force detection mechanism of the present disclosure is advantageous in that the sensor <NUM> and the annular magnet <NUM> not only sense the rotation speed of the crankshaft <NUM> but also sense and determine whether the crankshaft <NUM> is rotating. It is only when the crankshaft <NUM> rotates and the torque generated by the torque F is greater than or equal to the predetermined torque that the auxiliary power assembly <NUM> supplies auxiliary power to preclude unintended acceleration.

Claim 1:
A pedal force detection mechanism for an electric-assisted bicycle, adapted to be received in a shaft housing (<NUM>) of the electric-assisted bicycle to coordinate with a crankshaft (<NUM>) and connect to an auxiliary power assembly (<NUM>), with the crankshaft (<NUM>) movably disposed at the shaft housing (<NUM>), the pedal force detection mechanism comprising:
a torque-transmitting member (<NUM>) for transmitting a torque of the crankshaft (<NUM>) unidirectionally and diverting the torque along an axial direction of the crankshaft (<NUM>); and
a main thrust bearing (<NUM>) for abutting against the torque-transmitting member (<NUM>) to transmit the diverted torque;
characterized by the pedal force detection mechanism further comprising:
a strain sensing assembly (<NUM>) having a strain gauge (<NUM>), a resilient ring-shaped base (<NUM>) and a supporting annular base (<NUM>), with the supporting annular base (<NUM>) disposed outside the torque-transmitting member (<NUM>) and abutting against the shaft housing (<NUM>), allowing an axial-strain gap (<NUM>) to be defined between the supporting annular base (<NUM>) and the main thrust bearing (<NUM>), the resilient ring-shaped base (<NUM>) being disposed outside the supporting annular base (<NUM>) and fitted between the main thrust bearing (<NUM>) and the supporting annular base (<NUM>), the strain gauge (<NUM>) being disposed at the resilient ring-shaped base (<NUM>) and in signal connection with the auxiliary power assembly (<NUM>); and
a main drive gear (<NUM>) movably disposed between the crankshaft (<NUM>) and the shaft housing (<NUM>) and having a main gear (<NUM>), an internally-connected ring body (<NUM>) and an externally-connected ring body (<NUM>), the internally-connected ring body (<NUM>) being integrally formed with the main gear (<NUM>) and located on an inner side of the main gear (<NUM>), the externally-connected ring body (<NUM>) being fixedly connected to an outer side of the main gear (<NUM>), wherein the torque-transmitting member (<NUM>) and the internally-connected ring body (<NUM>) rotate synchronously, and an axial-movement gap (<NUM>) is defined between the torque-transmitting member (<NUM>) and the internally-connected ring body (<NUM>).