Bicycle transmission control device

A bicycle transmission control device is basically provided with a transmission controller that is programmed to switch between a first control state and a second control state. The bicycle transmission control device operates in accordance with the first control state for controlling a transmission based on a first signal that is input from a first detector, which detects a rotation of a crank. The bicycle transmission control device operates in accordance with the second control state for controlling the transmission based on a second signal that is input from a second detector, which detects a value reflecting a bicycle speed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2014-207513, filed on Oct. 8, 2014 and Japanese Patent Application No. 2015-110716, filed on May 29, 2015. The entire disclosures of Japanese Patent Application No. 2014-207513 and Japanese Patent Application No. 2015-110716 are hereby incorporated herein by reference.

BACKGROUND

Field of the Invention

This invention generally relates to a bicycle transmission control device. More specifically, the present invention relates to a bicycle transmission control device for changing a gear ratio of a transmission.

Background Information

Some bicycles are provided with an automatic gear changing mode that is controlled by a bicycle transmission control device for changing a gear ratio of a transmission. One example of a conventional bicycle transmission control device is disclosed in Japanese Laid-Open Patent Publication No. 1997-123978. In this conventional bicycle transmission control device, the transmission is controlled based only on signals output from either a cadence sensor or a vehicle speed sensor so that the rotational speed of a crank is maintained for a certain range.

SUMMARY

Generally, the present disclosure is directed to various features of a bicycle transmission control device. In the above mentioned conventional bicycle transmission control device, there is a risk that the gear ratio is changed at an inappropriate time depending on the traveling state of the bicycle.

One object of the present invention is to provide a bicycle transmission control device that is configured to change the gear ratio at an appropriate time as compared to the conventional technology.

In view of the state of the known technology and in accordance with a first aspect of the present disclosure, a bicycle transmission control device is provided that basically comprises a transmission controller that is programmed to switch between a first control state and a second control state. The bicycle transmission control device operates in accordance with the first control state for controlling a transmission based on a first signal that is input from a first detector, which detects a rotation of a crank. The bicycle transmission control device operates in accordance with the second control state for controlling the transmission based on a second signal that is input from a second detector, which detects a value reflecting a bicycle speed.

In accordance with a second aspect of the present invention, the bicycle transmission control device according to the first aspect is configured so that the second detector detects a rotation of a wheel of the bicycle.

In accordance with a third aspect of the present invention, the bicycle transmission control device according to the first or second aspect is configured so that the first control state and the second control state are switched based on the first signal and the second signal.

In accordance with a fourth aspect of the present invention, the bicycle transmission control device according to the first or second aspect is configured so that the first control state and the second control state are switched based on the first signal, the second signal and a manual drive force that is applied to the crank.

In accordance with a fifth aspect of the present invention, the bicycle transmission control device according to the first or second aspect is configured so that the first control state and the second control state are switched based on a manual drive force that is applied to the crank.

In accordance with a sixth aspect of the present invention, the bicycle transmission control device according to the third aspect is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission based on the first signal when a rotational speed of the crank based on the first signal is greater than or equal to a maximum rotational speed of the crank based on the second signal.

In accordance with a seventh aspect of the present invention, the bicycle transmission control device according to the third or sixth aspect is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission based on the second signal when a maximum rotational speed of the crank based on the second signal is greater than a rotational speed of the crank based on the first signal.

In accordance with an eighth aspect of the present invention, the bicycle transmission control device according to the fourth aspect is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission based on the second signal when a maximum rotational speed of the crank based on the second signal is greater than the rotational speed of the crank based on the first signal, and the manual drive force is less than a prescribed value.

In accordance with a ninth aspect of the present invention, the bicycle transmission control device according to the fourth or eighth aspect is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission based on the first signal when a maximum rotational speed of the crank based on the second signal is greater than the rotational speed of the crank based on the first signal, and the manual drive force is greater than or equal to a prescribed value.

In accordance with a tenth aspect of the present invention, the bicycle transmission control device according to the fifth aspect is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission based on the first signal when the manual drive force is greater than or equal to a prescribed value.

In accordance with an eleventh aspect of the present invention, the bicycle transmission control device according to the fifth or tenth aspect is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission based on the second signal when the manual drive force is less than a prescribed value.

In accordance with a twelfth aspect of the present invention, the bicycle transmission control device according to any one of the fourth, fifth and eighth to eleventh aspects is configured so that the manual drive force is obtained based on the third signal that is input from a drive force sensor that outputs the third signal in response to a manual drive force that is applied to the crank.

In accordance with a thirteenth aspect of the present invention, the bicycle transmission control device according to any one of the first to twelfth aspects is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission when controlling the transmission based on the first signal so that the rotational speed of the crank based on the first signal will be a prescribed crank rotational speed or a crank rotational speed within a prescribed range.

In accordance with a fourteenth aspect of the present invention, the bicycle transmission control device according to any one of the first to thirteenth aspects is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission when controlling the transmission based on the second signal so that the maximum rotational speed of the crank based on the second signal will be a prescribed crank rotational speed or a crank rotational speed within a prescribed range.

In accordance with a fifteenth aspect of the present invention, the bicycle transmission control device according to the fourteenth aspect is configured so that the maximum rotational speed of the crank based on the second signal is obtained based on the second signal, information related to a gear ratio, and information related to at least one of a wheel diameter, a wheel radius, or a wheel circumference.

In accordance with a sixteenth aspect of the present invention, the bicycle transmission control device according to any one of the first to fifteenth aspects is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission based on the second signal when an abnormality has occurred with the first signal.

In accordance with a seventeenth aspect of the present invention, the bicycle transmission control device according to any one of the first to sixteenth aspects is configured so that the transmission controller is further programmed to output a control signal for controlling the transmission based on the first signal when an abnormality has occurred with the second signal.

In accordance with an eighteenth aspect of the present invention, the bicycle transmission control device according to the second aspect, or any one of the third to seventeenth aspects having the second aspect, is configured so that the first detector detects a minimum angle in one rotation of the crank that is smaller than a minimum angle in one rotation of the wheel that can be detected by the second detector.

In accordance with a nineteenth aspect of the present invention, the bicycle transmission control device according to any one of the first to eighteenth aspects is configured so that the transmission controller is further configured to operate the transmission so that the gear ratio becomes greater when the transmission is controlled based on the first signal and when the rotational speed of the crank is greater than or equal to a first upper limit value. The transmission controller is further configured to operate the transmission so that the gear ratio becomes smaller when the transmission is controlled based on the first signal and when the rotational speed of the crank is less than or equal to a first lower limit value. The transmission controller is further configured to operate the transmission so that the gear ratio becomes greater when the transmission is controlled based on the second signal and when the maximum rotational speed of the crank corresponding to the second signal is greater than or equal to a second upper limit value. The transmission controller is further configured to operate the transmission so that the gear ratio becomes smaller when the transmission is controlled based on the second signal and when the maximum rotational speed of the crank corresponding to the second signal is less than or equal to a second tower limit value.

In accordance with a twentieth aspect of the present invention, the bicycle transmission control device according to the nineteenth aspect is configured so that the transmission controller is further configured to set the second upper limit value to be less than the first upper limit value.

In accordance with a twenty-first aspect of the present invention, the bicycle transmission control device according to the nineteenth or twentieth aspect is configured so that the transmission controller is further configured to set the second lower limit value to be greater than the first lower limit value.

In accordance with a twenty-second aspect of the present invention, the bicycle transmission control device according to any one of the nineteenth to twenty-first aspects is configured so that the transmission controller is further configured to set a range between the second upper limit value and the second lower limit value to be 25 to 50% of a range between the first upper limit value and the first lower limit value.

In accordance with a twenty-third aspect of the present invention, the bicycle transmission control device according to any one of the nineteenth to twenty-second aspects is configured so that the transmission controller is further configured to not operate the transmission when the rotational speed of the crank reaches a range below the first upper limit value and above the first lower limit value during a period from when the rotational speed of the crank is greater than or equal to the first upper limit value or less than or equal to the first lower limit value until when a first standby period elapses, when the transmission is controlled based on the first signal. Also the transmission controller is further configured to not operate the transmission when the rotational speed of the crank reaches a range below the second upper limit value and above the second lower limit value during a period from when the maximum rotational speed of the crank is greater than or equal to the second upper limit value or less than or equal to the second lower value until when a second standby period elapses, when the transmission is controlled based on the second signal.

In accordance with a twenty-fourth aspect of the present invention, the bicycle transmission control device according to the twenty-third aspect is configured so that the transmission controller is further configured to set the second standby period to be less than or equal to the first standby period.

In accordance with a twenty-fifth aspect of the present invention, the bicycle transmission control device according to the twenty-third aspect is configured so that the transmission controller is further configured to set the first standby period and the second standby period based on a travel load of the bicycle.

In accordance with a twenty-sixth aspect of the present invention, the bicycle transmission control device according to the twenty-fifth aspect is configured so that the transmission controller is further configured to set the second standby period to be less than or equal to the first standby period when the travel load of the bicycle is included in the same range.

In accordance with a twenty-seventh aspect of the present invention, the bicycle transmission control device according to the twenty-sixth aspect is configured so that the transmission controller is further configured to not operate the transmission the first standby period and the second standby period are set based on a previous shifting operation of the transmission and the travel load of the bicycle.

With the above configurations, the bicycle transmission control device is configured to change the gear ratio at an appropriate time as compared to the conventional technology.

Also other objects, features, aspects and advantages of the disclosed bicycle transmission control device will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses illustrative embodiments of the bicycle transmission control device.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring initially toFIG. 1, a bicycle10is illustrated that is equipped with a bicycle transmission control device in accordance with a first embodiment. The bicycle10comprises a frame12, a handlebar14, a front wheel16, a rear wheel18and a drive mechanism20, a gear changing control apparatus22, a gear shifting device24, a first detection device26(seeFIG. 2), a second detection device28(seeFIG. 2) and a drive force sensor30. The drive mechanism20comprises a front sprocket34, a rear sprocket36, a chain38, a pair of cranks42and a pair of pedals44.

The bicycle transmission control device basically comprises a gear changing state detection device68(seeFIG. 2) and a control device70. The control device70constitutes a transmission controller that includes at least one processor and at least one memory device with one or more control programs prestored therein. The bicycle transmission control device further comprises the first detection device26, the second detection device28and the drive force sensor30. The first detection device26, the second detection device28and the drive force sensor30output detection signals to the control device70as explained below.

The crank42comprises a crankshaft40that is rotatably supported by the frame12and left and right cranks42. Each of the left and right pedals44comprises a pedal shaft46. The left and right cranks42are attached to a crankshaft40. The main body of the pedal44is rotatably attached to the crank42about the pedal shaft46.

The front sprocket34is coupled to the crankshaft40. The front sprocket34is provided coaxially with the crankshaft40. The front sprocket34can be coupled so as to not rotate relatively with the crankshaft40or via a one-way clutch (diagram omitted) so that the front sprocket34will roll forward when the crankshaft40rolls forward.

The rear sprocket36is rotatably attached around an axle18A of the rear wheel18. The rear sprocket36is coupled with the rear wheel18via a one-way clutch. The chain38is wound onto the front sprocket34and the rear sprocket36. When the cranks42rotate due to a manual drive three that is applied to the pedals44, the rear wheel18is rotated by the front sprocket34, the chain38, and the rear sprocket36.

The gear changing control apparatus22is attached to the handlebar14. The gear changing control apparatus22is electrically connected to the control device70by a cable that is not diagrammed. When the gear changing control apparatus22is operated by a rider, the gear changing control apparatus22transmits an upshift signal or a downshift signal to the control device70. Upshifting is a shift in the direction that increases the gear ratio γ, and downshifting is a shift in the direction that decreases the gear ratio γ.

As shown inFIG. 2, the gear shifting device24comprises a motor unit48and a transmission50. The transmission50is realized by an internal transmission that is integrated with a hub of the rear wheel18(refer toFIG. 1). The transmission50is formed comprising a planetary gear mechanism that is controlled by the motor unit48. The transmission50changes the gear ratio γ in a stepwise manner. The motor unit48changes the gear ratio γ by changing the coupling state of the gears that form the planetary gear mechanism of the transmission50. The motor unit48is electrically connected to the control device70by a cable that is not diagrammed. The motor unit48comprises an electric motor and a reduction gear for reducing the output rotation of the electric motor. The electric motor is connected to the transmission50via the reduction gear.

The first detection device26detects the rotation of one of the cranks42(refer toFIG. 1). The first detection device26comprises two magnets52A and52B, as well as a first detector54that is attached to the frame12. The magnet52A is an annular magnet, in which several magnetic poles are alternately arranged side by side in the circumferential direction. The magnet52A is provided to the crankshaft40or one of the cranks42, and is disposed coaxially with the crankshaft40. The magnet52B is attached to one of the left and right cranks42.

The first detector54is electrically connected to the control device70by a cable that is not diagrammed. The first detector54transmits a first signal S1to the control device70in response to the rotation of the cranks42. The first detector54is a so-called cadence sensor. The first detector54comprises an element56A and an element56B. The element56A detects a relative angular position of one of the cranks42with respect to the frame12. The element56A outputs a value corresponding to changes in the magnetic field of the magnet52A. The element56B detects the magnetic field of the magnet52B. The element56B detects a reference angular position of one of the cranks42with respect to the frame12.

The first detector54further comprises a first rotational speed calculation unit58. The first rotational speed calculation unit58includes a processor that calculates the rotational speed of the cranks42per unit of time (hereinafter referred to as the “first rotational speed NA”) from the output of the elements56A and56B. The first detector54outputs a first signal S1comprising information that represents the first rotational speed NA to the control device70. The element56A outputs a signal in which one cycle is the angle obtained by dividing 360° by the number of magnetic poles with the same polarity when the crankshaft makes one rotation. The element56B outputs a signal in which one cycle is one rotation of the crankshaft40.

The element56B outputs a value corresponding to the rotational angle of the one of the cranks42(refer toFIG. 1). The minimum angle of one of the cranks42(refer toFIG. 1) that can be detected by the first detector54is less than or equal to 180 degrees, preferably fifteen degrees, and more preferably six degrees.

The second detection device28detects the rotation of the front wheel16, which is the wheel on the front side (refer toFIG. 1). The second detection device28comprises a magnet60that is attached to one of the spokes16A of the front wheel16and a second detector62that is attached to a front fork12A of the frame12. The magnet60can be attached to one of the spokes18B of the rear wheel18. In this case, the second detector62is attached to a chain stay of the frame12. The second detector62is fixed to the frame12by a bolt and nut, a band, etc. In the description below, the second detector62is configured to detect the rotation of the front wheel16, but a case in which the second detector62detects the rotation of the rear wheel18, only replacing the front wheel16with the rear wheel18, is possible; therefore, the description thereof will be omitted.

The second detector62is electrically connected to the control device70by a cable that is not diagrammed. The second detector62transmits a second signal S2to the control device70in response to the rotation of the front wheel16. The second detector62is a so-called vehicle speed sensor. The second detector62comprises an element64and a vehicle speed calculation unit66. The element64outputs a value corresponding to changes in the relative position with the magnet60. The vehicle speed calculation unit66includes a processor that calculates the travel distance per unit of time (hereinafter referred to as the “vehicle speed V”) from the output of the element64.

The element64outputs a signal in which one cycle is one rotation of the front wheel16(refer toFIG. 1). That is, the minimum angle of the front wheel16that can be detected by the second detector62is 360 degrees. The detectable minimum angle in one rotation of the cranks42is smaller than the detectable minimum angle in one rotation of the front wheel16.

The vehicle speed calculation unit66calculates the vehicle speed V by multiplying the circumferential length (hereinafter referred to as the “circumferential length L”) of the front wheel16(refer toFIG. 1) by the rotational speed of the front wheel16(refer toFIG. 1) per unit of time. The circumferential length L of the front wheel16is stored in advance in the memory device of the second detector62. The second detector62outputs a second signal S2comprising information related to the vehicle speed V to the control device70. Calculating the vehicle speed V using the diameter or the radius of the front wheel16(refer toFIG. 1) is also possible. In this case, the diameter or the radius of the front wheel16(refer toFIG. 1) is stored in advance in the memory device of the second detector62.

The gear changing state detection device68detects the current gear changing state of the gear shifting device24. The gear changing state detection device68may be provided to the motor unit48or to the gear changing control apparatus22. The gear changing state detection device68outputs information related to the shift position, that is, the gear ratio γ. The gear changing state detection device68detects the rotation angle of a prescribed portion of the electric motor or the deceleration device in the motor unit48, the rotation angle of a prescribed position of the transmission50, etc. The gear changing state detection device68is comprised of a potentiometer or a detection device comprising a magnet and a magnetic sensor that detects this magnet, etc. The gear changing state detection device68is electrically connected to the control device70.

The drive force sensor30detects a manual drive force that is applied to one of the cranks42(refer toFIG. 1). The drive force sensor30outputs a third signal S3that includes a signal corresponding to the manual drive force. The drive force sensor30can be provided between the crankshaft40shown inFIG. 1to the front sprocket34, the crankshaft40, the front sprocket34, the cranks42, or the pedals44. The drive force sensor30may be realized using, for example, a strain sensor, a magnetostrictive sensor, an optical sensor, or a pressure sensor, and any sensor may be employed as long as the sensor outputs a signal corresponding to the manual drive force that is applied to the cranks42or the pedal s44.

As shown inFIG. 2, the control device70comprises a second rotational speed calculation unit72, a rotational speed comparing unit74, a drive force calculation unit76, a selection value setting unit78, a gear shift determination unit80, and a motor controller82. The control device70is formed comprising an arithmetic processor such as a CPU and a memory device to which software is stored and is configured to realize a plurality of functions. The second rotational speed calculation unit72, the rotational speed comparing unit74, the drive force calculation unit76, the selection value setting unit78, the gear shift determination unit80, and the motor controller82represent the functions of the control device70. The control device70can comprise a plurality of arithmetic processors and a plurality of microcomputers. The second signal S2is input to the second rotational speed calculation unit72. The first signal S1is input to the rotational speed comparing unit74and the selection value setting unit78.

The second rotational speed calculation unit72estimates the second rotational speed NB of one of the cranks42based on the second signal S2from the second detector62, information related to the circumferential length L of the front wheel16(refer toFIG. 1), and the gear ratio γ at that time. Specifically, the second rotational speed calculation unit72calculates the second rotational speed NB by dividing the vehicle speed V that is included in the second signal S2by the circumferential length of the front wheel16and the gear ratio γ. The second rotational speed calculation unit72outputs the second rotational speed NB to the rotational speed comparing unit74. The relationship between the gear ratio γ and the detection results of the gear changing state detection device68is set in advance, and such a relationship is stored in the memory. The second rotational speed calculation unit72performs a calculation using the corresponding gear ratio γ or obtains the gear ratio γ by using a function from the detection results of the gear changing state detection device68.

The rotational speed of the front wheel16(refer toFIG. 1) may be greater than a value obtained by multiplying the gear ratio by the rotational speed of the cranks42. For example, there are cases in which the front wheel16is rotating even when the cranks42are stopped, such as when traveling downhill. For this reason, there are cases when the second rotational speed NB that is calculated based on the output of the second detector62is a value that is greater than the first rotational speed NA. Additionally, since the detectable minimum angle in one rotation of the front wheel16is larger than the detectable minimum angle in one rotation of the cranks42, there are cases in which a delay occurs in the calculation of the second rotational speed NB, and the calculated second rotational speed NB is a value that is greater than the first rotational speed NA. The second rotational speed NB corresponds to the rotational speed of the cranks42when the cranks42and the front wheel16are rotating in sync, that is, to the maximum rotational speed of the cranks42.

The rotational speed comparing unit74compares the first rotational speed NA that is represented by information included in the first signal S1and the second rotational speed NB that is represented by information included in a signal output from the second rotational speed calculation unit72. The rotational speed comparing unit74outputs either the first rotational speed NA or the second rotational speed NB, based on which is greater, to the selection value setting unit78. The drive force calculation unit76calculates the manual drive force T based on the third signal S3from the drive force sensor30and outputs the manual drive force T to the selection value setting unit78. The first rotational speed NA and the second rotational speed NB are input to the selection value setting unit78. The selection value setting unit78sets the first rotational speed NA or the second rotational speed NB as the selection value N, based on the comparison results of the rotational speed comparing unit74and the manual drive force T or based only on the comparison results of the rotational speed comparing unit74, and outputs the selection value N to the gear shift determination unit80.

The control device70switches between a first control state for controlling the transmission50based on the first signal S1and the second control state for controlling the transmission50based on the second signal S2. The control device70switches between the first control state and the second control state based on the first rotational speed NA, the second rotational speed NB, and the manual drive force T.

The switching operation of the control state by the control device70will be described with reference toFIG. 3.

In step S11, the second rotational speed calculation unit72calculates the second rotational speed NB based on the vehicle speed V. Next, in step S12, the selection value setting unit78compares the first rotational speed NA and the second rotational speed NB, proceeds to step S13when the first rotational speed NA is greater than or equal to the second rotational speed NB, and sets the first rotational speed NA to the selection value N. When the first rotational speed NA is set to the selection value N in the previous switching operation, the selection value N is maintained at the first rotational speed NA. When the second rotational speed NB is set to the selection value N in the previous switching operation, the selection value N is changed from the second rotational speed NB to the first rotational speed NA, and the control state is switched from the second control state to the first control state.

If the second rotational speed NB is greater than the first rotational speed NA in step S12, the selection value setting unit78returns to step S14and determines whether or not the manual drive force T is greater than or equal to a prescribed value TX. When the manual drive force T is greater than or equal to the prescribed value TX, the operation proceeds to step S15and sets the first rotational speed NA to the selection value N. When the first rotational speed NA is set to the selection value N in the previous switching operation, the selection value N is maintained at the first rotational speed NA. When the second rotational speed NB is set to the selection value N in the previous switching operation, the selection value N is changed from the second rotational speed NB to the first rotational speed NA, and the control state is switched from the first control state to the second control state.

When the manual drive force T is less than the prescribed value TX in step S14, the selection value setting unit78proceeds to step S16and sets the second rotational speed NB to the selection value N. When the second rotational speed NB is set to the selection value N in the previous switching operation, the selection value N is maintained at the second rotational speed NB. When the first rotational speed NA is set to the selection value N in the previous switching operation, the selection value N is changed from the first rotational speed NA to the second rotational speed NB, and the control state is switched from the second control state to the first control state. For example, a value between 1 Nm-3 Nm is selected as the prescribed value TX.

The gear shift determination unit80shown inFIG. 2outputs an upshift signal or a downshift signal to the motor controller82based on the selection value N that is set in the selection value setting unit78. The gear shift determination unit80can read a first determination value NX and a second determination value NY stored in a storage unit84(i.e., a memory device). The first determination value NX and the second determination value NY are threshold values. The gear shift determination unit80outputs an upshift signal when the selection value N is greater than or equal to the first determination value NX and outputs a downshift signal when the selection value N is less than or equal to the second determination value NY. Preferably, a value that is greater than or equal to the second determination value NY is selected as the first determination value NX. For example, 65 rpm-70 rpm is selected as the first determination value NX, and, for example, a value between 60 rpm-65 rpm is selected as the second determination value.

The first determination value NX and the second determination value NY are set as values at which the transmission50is controlled so that the selection value N will be a prescribed crank rotational speed or a crank rotational speed within a prescribed range. In other words, the gear shift determination unit80controls the transmission50so that the first rotational speed NA will be a prescribed crank rotational speed or a crank rotational speed within a prescribed range when controlling the transmission50based on the first signal S1. Additionally, the gear shift determination unit80controls the transmission50so that the second rotational speed NB will be a prescribed crank rotational speed or a crank rotational speed within a prescribed range when controlling the transmission50based on the second signal S2.

The procedure for the shifting operation that is executed by the gear shift determination unit80will be described with reference toFIG. 4. The gear shift determination unit80determines whether or not the selection value N is greater than the first determination value NX in step S21. When the selection value N is greater than the first determination value NX, the gear shift determination unit generates an upshift signal and outputs this to the motor controller82in step S22.

When the selection value N is less than the first determination value NX in step S21, the gear shift determination unit80determines whether or not the selection value N is less than or equal to the second determination value NY in step S23. When the selection value N is less than or equal to the second determination value NY, the gear shift determination unit80generates a downshift signal and outputs this to the motor controller82in step S24.

When the selection value N is greater than the second determination value NY in step S23, the gear shift determination unit80does not output an upshift signal or a downshift signal to the motor controller82.

The motor controller82shown inFIG. 2controls the motor unit48based on a signal output from the gear shift determination unit80or a signal that is input from the gear changing control apparatus22. The motor controller82outputs a control signal SA for shifting the shift position of the gear changing device24up to the drive circuit (diagram omitted) of the motor unit48when an upshift signal is input. The motor controller82outputs a control signal SA for shifting the shift position of the gear changing device24down to the drive circuit (diagram omitted) of the motor unit48when a downshift signal is input. When an upshift signal is input at the time of the maximum gear ratio γ, and when a downshift signal is input at the time of the minimum gear ratio γ, the motor controller82will not drive the motor unit48.

The action and effects of the control device70will be described.

(1) The minimum angle of the cranks42that can be detected by the first detector54is smaller than the minimum angle of the front wheel16that can be detected by the second detector62. That is, the first rotational speed NA that is calculated according to the output of the first detector54is more accurate than the second rotational speed NB that is calculated according to the output of the second detector62. For this reason, more appropriately changing the transmission50than when controlling the transmission50, based on the second rotational speed NB, is possible by controlling the transmission50based on the first rotational speed NA.

If the transmission50is controlled based only on the first rotational speed NA, for example, when the rotation of the cranks42is stopped while the bicycle10is traveling, the transmission wilt be controlled to downshift so that the gear ratio γ will be decreased. In this case, a situation arises immediately after the rider restarts the rotation of the cranks42in which the manual drive force is not immediately transmitted to the wheels due to the gear ratio γ being too small, and having the rotational speed of the cranks42fit within the prescribed range becomes difficult.

The control device70is configured to automatically switch between a first control state for controlling the transmission50based on the first signal S1and the second control state for controlling the transmission50based on the second signal S2. For this reason, controlling the gear ratio γ based on signals S1and S2that are suitable as traveling situations, etc., of the bicycle10is possible. As a result, changing the gear ratio γ at an appropriate time is possible.

(2) For example, the accuracy of the second rotational speed NB that is calculated according to the output of the second detector62is less accurate than the first rotational speed NA that is calculated according to the output of the first detector54. For this reason, there are cases in which the second rotational speed NB becomes greater than the first rotational speed NA even when the crank42and the front wheel16are actually rotating in sync, especially when the vehicle speed is suddenly increased or decreased.

When controlling the gear shifting device24only by comparing the second rotational speed NB and the first rotational speed NA, there are cases in which the gear ratio γ becomes large by gear shifting based on the second rotational speed NB, even if the crank42and the front wheel16are actually rotating in sync.

The control device70controls the transmission50based on the first rotational speed NA when the manual drive force T is greater than or equal to a prescribed value TX, even if the second rotational speed NB is greater than the first rotational speed NA. For this reason, controlling the bicycle according to the load of the rider is possible, and preventing an inappropriate gear ratio γ is possible even if the vehicle speed changes rapidly.

Second Embodiment

The configuration of a control device70according to the second embodiment is explained with reference toFIG. 5. The control device70of the second embodiment executes a shifting operation shown inFIG. 5, instead of a shifting operation of the first embodiment shown inFIG. 4. The shifting operation shown inFIG. 5is repeated until powering off. Also, the storage unit84(refer toFIG. 2) stores a first upper limit value NA1, a first lower limit value NA2, a second upper limit value NB1, a second lower limit value NB2, and a table related to a first standby period PA and a second standby period PB, instead of the determination value NX, NY. The first upper limit value NA1, the first lower limit value NA2, the second upper limit value NB1, the second tower limit value NB2, the first standby period PA, and the second standby period PB are threshold values. The common configurations with the first embodiment are indicated with the same reference symbols as in the first embodiment and their descriptions will be omitted.

The procedure of the shifting operation executed by a gear shift determination unit80is explained.

The gear shift determination unit80determines whether or not a selection value N selected by a selection value setting unit78in step S31is a first rotational speed NA.

When the selection value N is the first rotational speed NA, the gear shift determination unit80determines whether or not the selection value N is greater than or equal to the first upper limit value NA1 in step S31. When the selection value N is greater than or equal to the first upper limit value NA1, the gear shift determination unit80determines whether or not the first standby period PA has elapsed from a previous shifting in step S33. The previous shifting is when either an upshift signal or a downshift signal was output to a transmission50the last time. When the control device70outputs an upshift signal and a downshift signal to the transmission50, the control device70counts up elapsed time from this moment.

When the first standby period PA has elapsed from the previous shifting, the gear shift determination unit80generates an upshift signal and outputs this to a motor controller82in step S34. When the first standby period PA has not elapsed in step S33, the gear shift determination unit80does not output an upshift signal or a downshift signal to the motor controller82.

When the selection value N is less than the first upper limit value NA1 in step S32, the gear shift determination unit80determines whether or not the selection value N is less than or equal to the first lower limit value NA2 in step S35. When the selection value N is greater than the first lower limit value NA2 in step S35, the gear shift determination unit80does not output an upshift signal or a downshift signal to the motor controller82. That is, when the first rotational speed NA is less than the first upper limit value NA1 and greater than the first lower limit value NA2 in a first control state, the gear shift determination unit80does not output an upshift signal or a downshift signal to the motor controller87.

When the selection value N is less than or equal to the first tower limit value NA2 in step S35, the gear shift determination unit80determines whether or not the first standby period PA has elapsed from the previous shifting in step S36.

When the first standby period PA has elapsed from the previous shifting, the gear shift determination unit80generates a downshift signal and outputs this to the motor controller82in step S37. When the first standby period PA has not elapsed in step S36, the gear shift determination unit80does not output an upshift signal or a downshift signal to the motor controller82.

That is, the control device70operates the transmission50on that the gear ratio γ becomes greater when the transmission50is controlled based on a first signal and when the first rotational speed NA, which is a rotational speed of a crank32, is greater than or equal to the first upper limit value NA1, and operates the transmission so that the gear ratio γ becomes smaller when the transmission50is controlled based on the first signal and when the first rotational speed NA is less than or equal to the first lower limit value.

Also, the control device70does not operate the transmission50when the rotational speed of the crank reaches a range below the first upper limit value NA1 and above the first lower limit value NA2 during a period from when the first rotational speed NA is greater than or equal to the first upper limit value NA1 or less than or equal to the first lower limit value NA2 until when the first standby period PA elapses, when the transmission50is controlled based on the first signal.

When the selection value N is a second rotational speed NB in step S31, the gear shift determination unit80determines whether or not the selection value N is greater than or equal to the second upper limit value NB1 in step S38. When the selection value N is greater than or equal to the second upper limit value NB1, the gear shift determination unit80determines whether or not the second standby period PB has elapsed from the previous shifting in step S39. When the second standby period PB has elapsed, the gear shift determination unit80generates an upshift signal and outputs this to the motor controller82in step S40. When the second standby period PB has not elapsed in step S39, the gear shift determination unit80does not output an upshift signal or a downshift to the motor controller82.

When the selection value N is less than the second upper limit value NB1in step S38, the gear shift determination unit80determines whether or not the selection value N is less than or equal to the second lower limit value NB2 in step S41. When the selection value N is greater than the second lower limit value NB2 in step S42, the gear shift determination unit80does not output an upshift signal or a downshift signal to the motor controller82. That is, when the second rotational speed NB is less than the second upper limit value NB1 and greater than the second lower limit value NB2 in a second control state, the gear shift determination unit80does not output an upshift signal or a downshift signal to the motor controller82.

When the selection value N is less than or equal to the second lower limit value NB2 in step S41, the gear shift determination unit80determines whether or not the second standby period PB has elapsed from the previous shifting in step S36. When the second standby period PB has elapsed, the gear shift determination unit80generates a downshift signal and outputs this to the motor controller82in step S43. When the second standby period PB has not elapsed in step S43, the gear shift determination unit80does not output upshift signal or a downshift signal to the motor controller82.

That is, the control device70operates the transmission50so that the gear ratio γ becomes greater when the transmission50is controlled based on the second signal and when the second rotational speed NB is greater than or equal to the second upper limit value NB1, and operates the transmission50so that the gear ratio γ becomes smaller when the transmission50is controlled based on the second signal and when the second rotational speed NB is less than or equal to the second lower limit value NB2.

Also, the control device70does not change the gear ratio γ when the rotational speed of the crank reaches a range below the second upper limit value NB1 and above the second lower limit value NA2 during a period from when the second rotational speed NB is greater than or equal to the second upper limit value NB1 or less than or equal to the second lower limit value NB2 until when the second standby period PB elapses, when the transmission is controlled based on the second signal.

The storage unit84stores the first upper limit value NA1, the first lower limit value NA2, the second upper limit value NB1, and the second lower limit value NB2. The second upper limit value NB1 is less than the first upper limit value NA1. The second lower limit value NB2 is greater than the first lower limit value NA2. Preferably, a range between the second upper limit value NB1 and the second lower limit value NB2 is 25-50% of a range between the first upper limit value NA1 and the first lower limit value NA2. For example, the first upper limit value NA1 is 70 rpm, the first lower limit value NA2 is 50 rpm, the second upper limit value NB1 is 67.5 rpm, and the second lower limit value NB2 is 52.5 rpm.

The storage unit84stores the table related to the first standby period PA and the second standby period PB. The first standby period PA and the second standby period PB are set based on a control state, a magnitude of a travel load R, and a previous shifting operation. The travel load R is calculated based on at least one of a manual drive force that is applied to a pedal44, a bicycle speed of a bicycle10, and a rotational speed of the crank32. The travel load R is obtained, for example, by subtracting a changed kinetic energy of the bicycle from an input energy. The input energy is obtained by integrating a torque on the crank caused by the manual drive force applied to the pedal44and the rotational speed of the crank. The changed kinetic energy of the bicycle is obtained from a weight of the bicycle and a rider and the bicycle speed of the bicycle. The changed kinetic energy of the bicycle is obtained, for example, from 1/2 m(v2−V1)2. The bicycle speed of the bicycle10can use the first rotational speed NA. The rotational speed of the crank32can use the second rotational speed NB. The travel load R comprises a first travel load RA and a second travel load RB. The first travel load RA is, for example, a relatively small travel load R such as when the bicycle10travels downhill. The second travel load RB is, for example, a relatively big travel load R such as when the bicycle10travels uphill. The second travel load RB is greater than the first travel load RA.

Table 1 shows a control state, a first travel load RA, and a previous shifting operation, and a relation table between a first standby period PA and a second standby period PB when an upshift condition is met. The upshift condition is met when the first rotational speed NA is greater than the upper limit value NA1 in the first control state and when the second rotational speed NB is greater than the upper limit value NB1 in the second control state.

A maximum period PA max, an intermediate period PAmid, and a minimum period PAmin of the first standby period PA holds a relationship of PAmax>PAmid>PAmin. A maximum period PBmax, an intermediate period PBmid, and a minimum period PBmin of the second standby period PB holds a relationship of PBmax>PBmid>PBmin. The maximum period PBmax can be equal to or different from the maximum period PAmax. The intermediate period PBmid can be equal to or different from the intermediate period PAmid. The minimum period PBmin can be equal to or different from the minimum period PAmin. The maximum period PAmax, PBmax is, for example, 1000 milliseconds. The intermediate period PAmid, PBmid is, for example, a period which is half of the maximum period PAmax, PBmax and is 500 milliseconds. The minimum period PAmin, PBmin is, for example, a period which is half of the intermediate period PAmid, PBmid and is 250 milliseconds.

When the upshift condition is met during the previous shifting operation which is upshifting and when the travel load R is greater than or equal to the first travel load RA, the control device70sets the first standby period PA or the second standby period PB to the maximum period PAmax or the maximum period PBmax. In other words, the control device70sets a period in which upshifting is prohibited to be longer when the travel load R is big, such as when the bicycle10performs downshifting while travelling on a flat road, than when the travel load R is small, such as when the bicycle10travels downhill.

Table 2 shows a control state, a second travel load RB, and a previous shifting operation, and a relation table between a first standby period PA and a second standby period PB when a downshift condition is met. The downshift condition is met when the first rotational speed NA is less than the lower limit value NA2 in the first control state and when the second rotational speed NB is less than the lower limit value NB2 in the second control state.

When the downshift condition is met during the previous shifting operation which is upshifting and when the travel load R is less than the second travel load RB, the control device70sets the first standby period PA or the second standby period PB to the maximum period PAmax or the maximum period PBmax. In other words, the control device70sets a period in which downshifting is prohibited to be longer when the travel load R is small, such as when the bicycle10performs upshifting while travelling on a flat road, than when the travel load R is big, such as after when the bicycle10performs upshifting while travelling uphill.

As shown in Table 1 and Table 2, the first standby period PA and the second standby period PB are set based on the previous shifting operation of the transmission50and the travel load R of the bicycle10. The second standby period PB is less than or equal to the first standby period PA when the travel load R of the bicycle10is included in the same range.

In addition to the effects of the first embodiment described in (1) and (2), the control device70will provide the following effects.

(3) The second upper limit value NB1 is different from the first upper limit value NA1. For this reason, the control device70can change the gear ratio γ using the upper limit value NA1, NB1 which is suitable to each of the first control state and the second control state.

(4) The second lower limit value NB2 is different from the first lower limit value NA2. For this reason, the control device70can change the gear ratio γ using the lower limit value NA2, NB2 which is suitable to each of the first control state and the second control state.

(5) The second upper limit value NB1 is less than the first upper limit value NA1. Also, the second lower limit value NB2 is greater than the first lower limit value NA2. That is, a range between the second upper limit value NB1 and the second lower limit value NB2 is smaller than a range between the first upper limit value NA1 and the first lower limit value NA2. For this reason, shifting is facilitated in the second control state, or specifically, when the rider stops and does not rotate the crank32or when the torque applied to the crank32is small such as when the first rotational speed NA is less than the second rotational speed NB. As a result, the rider hardly feels a sense of incongruity due to a shifting operation of the transmission50, compared with when shifting is performed white a torque applied to the crank32is big. Moreover, since a shifting operation is facilitated when a torque applied to the crank32is small, a frequency of a shifting operation failure due to a torque applied to the crank32being big can be lowered.

(6) When the gear ratio γ becomes greater, the rotational speed of the crank32tends to become smaller. For this reason, the downshift condition tends to be met immediately after the gear ratio γ becomes greater. Also, when the gear ratio γ becomes smaller, the rotational speed of the crank32tends to become greater. For this reason, the upshift condition tends to be met immediately after the gear ratio γ becomes smaller. When the upshift condition or the downshift condition is met, the control device70does not change the gear ratio γ until after the first standby period PA or the second standby period PB has elapsed from the previous shifting operation. As a result, repeated shifting operations within a short period of time can be prevented.

(7) The control device70sets the standby period PA, PB when the upshift condition is met to be smaller than the standby period PA, PB when the previous shifting operation is upshifting and when the downshift condition is met while the travel load R is greater than or equal to the first travel load RA. For this reason, upshifting is facilitated in a state in which the travel load R, is small, such as on downhill. As a result, the rider hardly feels a sense of incongruity due to a shifting operation of the transmission50and a frequency of a shifting operation failure can be lowered.

(8) The control device70sets the standby period PA, PB when the downshift condition is met to be smaller than the standby period PA, PB when the previous shifting operation is downshifting and when the upshift condition is met while the travel load R is less than the second travel load RB. For this reason, downshifting is facilitated in a state in which the travel load R is big, such as on uphill.

(9) When the travel load R is included in the same range, the second standby period PB is less than or equal to the first standby period PA. For this reason, shifting is facilitated in the second control state in which the second rotational speed NB is greater than the first rotational speed NA.

MODIFIED EXAMPLES

The specific form that the present control device can take is not limited to the forms illustrated in each of the above-described embodiments. The present control device can take various forms that are different from each of the above-described embodiments. The modified example of each of the above-described embodiments explained below is one example of the various forms that the present control device can take.

Changing the shifting operation of the second embodiment to the operation shown inFIG. 6is also possible. In this modified example, the storage unit84stores the first determination value NX and the second determination value NY. The gear shift determination unit80executes the operation of step S51to determine whether or not the selection value N is greater than or equal to the first determination value NX, instead of the operation of step S32. The gear shift determination unit80executes the operation of step S54to determine whether or not the selection value N is greater than or equal to the first determination value NX, instead of the operation of step S38. Also, the gear shift determination unit80executes the operation of step S52to determine whether or not the selection value N is less than or equal to the second determination value NY, instead of the operation of step S35. The gear shift determination unit80executes the operation of step S54to determine whether or not the selection value N is less than or equal to the second determination value NY, instead of the operation of step S41. The shifting operation shown inFIG. 6is repeated until powering off. The gear shift determination unit80advances to step S33when an affirmative determination is made in step S51, and advances to step S52when a negative determination is made in step S51. The gear shift determination unit80advances to step S36when an affirmative determination is made in step S52, and ends the shifting operation when a negative determination is made in step S52. The gear shift determination unit80advances to step S39when an affirmative determination is made in step S53, and advances to step S54when a negative determination is made in step S53. The gear shift determination unit80advances to step S42when an affirmative determination is made in step S54, and ends the shifting operation when a negative determination is made in step S54. In the operation shown inFIG. 6, threshold values, which are shifting conditions, are not changed at the time of shifting based on the first rotational speed NA and at the time of shifting based on the second rotational speed NB.

In the shifting operation of the second embodiment, steps S33, S36, S39and S42shown inFIG. 5may be omitted. That is, as shown inFIG. 7, the control device70outputs an upshift signal and ends the shifting operation when the selection value N is greater than or equal to the upper limit value NA1, NB1 in step S32and step S38. The control device70outputs a downshift signal and ends the shifting operation when the selection value N is greater than or equal to the lower limit value NA2, NB2 in step S35and step S41.

In the second embodiment, the control device70may obtain at least one of the first upper limit value NA1, the first lower limit value NA2, the second upper limit value NB1, and the second lower limit value NB2 by calculation. For example, the storage unit84stores the first upper limit value NA1 and the first lower limit value NA2. In the second control state, the control device70sets a value obtained by multiplying a first coefficient greater than or equal to “1” by the first upper limit value NA1 to be the second upper limit value NB1, and sets a value obtained by multiplying a second coefficient less than “1” by the second lower limit value NA2 to be the second lower limit value NB2.

In the second embodiment, the first standby period PA may be a constant value regardless of the travel load R and the previous shifting operation.

In the second embodiment, the second standby period PB may be a constant value regardless of the travel load R and the previous shifting operation.

In the second embodiment, the second standby period PB may be equal to the first standby period PA.

In the second embodiment, the second standby period PB may be set to be less than or equal to the first standby period regardless of the travel load R and the previous shifting operation.

In the second embodiment, the control device70may obtain at least one of the first standby period PA and the second standby period PB by calculation. For example, the storage unit84stores the maximum period Pmax. The control device70calculates the first standby period PA or the second standby period PB by multiplying a correction coefficient based on the control state, the travel load R, and the previous shifting operation by the maximum period Pmax.

In each of the embodiments, it is also possible to change the switching operation to the operation shown inFIG. 8. That is, the control device70switches between the first control state and the second control state based on the manual drive force T. Specifically, after the second rotational speed calculation unit72calculates the second rotational speed NB in step S61, the selection value setting unit78determines whether or not the manual drive force T is greater than or equal to the prescribed value TX in step S62. When the manual drive force T is greater than or equal to the prescribed value TX, the selection value setting unit78proceeds to step S63and sets the first rotational speed NA to the selection value N; when the manual drive force T is less than the prescribed value TX, the selection value setting unit78proceeds to step S64and sets the second rotational speed NB to the selection value N.

In the switching operations of each of the embodiments, it is also possible to omit the operations of step S14and step S15of the switching operation shown inFIG. 3. That is, as shown inFIG. 9, the control device70sets the first rotational speed NA to the selection value N when the first rotational speed NA is greater than or equal to the second rotational speed NB; the second rotational speed NB is set to the selection value N when the first rotational speed NA is less than the second rotational speed NB.

It is also possible to change the switching operation to the operation of the embodiments to the operation shown inFIG. 10is also possible. The control device70sets the first rotational speed NA to the selection value N in the initial setting. The control device70determines whether or not the first rotational speed NA is the selection value N in step S71. If the first rotational speed NA is the selection value N, the control device determines whether or not an abnormality has occurred in the first signal S1in step S72. When a determination is made that an abnormality has occurred in the first signal S1in step S72, the control device70switches the second rotational speed NB to the selection value N in step S73. Additionally, when a determination is made that an abnormality has not occurred in the first signal S1in step S72, the control device70maintains the selection value N at the first rotational speed NA, and the present operation ends.

When a determination is made that the first rotational speed NA is not the selection value N in step S71, that is, when the second rotational speed NB is the selection value N, the control device70maintains the selection value N at the second rotational speed NB, and the present operation ends.

A determination is made that an abnormality has occurred in the first signal S1when, for example, the first rotational speed NA included in the first signal S1does not change from a constant value or when the first rotational speed NA is excessively large, even when a determination can be made based on the second signal S2that the bicycle is in a traveling state. Examples of cases in which the first rotational speed NA does not change from a constant value even when the bicycle10is in a traveling state include the adhesion of contamination, such as dirt to the first detector54, a malfunctioning of the first detector54, the fatting of the magnets52A and52B from the crank42, and a disconnection of a telegraph line (diagram omitted) that connects the first detector54and the control device70. Additionally, an example of a case in which the first rotational speed NA is excessively large is a short-circuit failure inside of the first detector54, etc.

In the modified example shown inFIG. 10, the control device70may set the second rotational speed NB to the selection value N in the initial setting and switch the first rotational speed NA to the selection value N when an abnormality has occurred in the second signal S2. Whether to select the second rotational speed NB or the first rotational speed NA in the initial setting may be selected by the rider. In this case, a cycle computer, a personal computer, or the like comprising an input interface may be electrically connected to the control device70, and the initial setting may be performed via such a device.

Adding the operation of the modified example shown inFIG. 10to the switching operation show inFIG. 3is also possible. That is, the operations of step S51-S53are executed after step S13and step S15inFIG. 3, and the above-described operation of the modified example shown inFIG. 10is performed after step S16.

In the switching operation shown inFIG. 3, the processing order of the operations of step S12and step S14may be interchanged. In this case, for example, the control device70determines whether or not the manual drive force T is greater than or equal to a prescribed value TX in step S12; when the manual drive force T is greater than or equal to the prescribed value TX, the operation proceeds to step S13. Additionally, if the manual drive force T is less than the prescribed value TX in step S12, a determination is made regarding whether or not the first rotational speed NA is greater than or equal to the second rotational speed NB in step S14. When a determination is made that the first rotational speed NA is greater than or equal to the second rotational speed NB in step S14, the operation proceeds to step S15and sets the first rotational speed NA to the selection value N. When a determination is made that the first rotational speed NA is less than the second rotational speed NB in step S14, the operation proceeds to step S16and sets the second rotational speed NB to the selection value N.

In each of the embodiments, it is also possible to attach the magnet52A of the first detection device26to the pedal44.

In each of the embodiments, it is also possible to attach the first detector54of the first detection device26to the crank32and attaching the magnets52A and52B to the frame12. In this case, the first detector54transmits the first signal S1to the control device70by wireless communication.

In each of the embodiments, the output of the elements56A and56B of the first detection device26may be directly input to the control device70, or they may be input to the control device70after amplifying the output of the elements56A and56B. In this case, the control device70comprises the function of the first rotational speed calculation unit58, and the first rotational speed NA is calculated by the control device70.

In each of the embodiments, it is also possible to make the element56A of the first detection device26a rotational angle sensor that is attached around the crankshaft40.

In each of the embodiments, it is possible to form at least one of the elements56A,56A of the first detection device26or the element64of the second detection device28from an optical sensor.

In each of the embodiments, it is possible to modify the configuration so that the second detection device28is attached to a rear wheel18, which is a wheel on the rear side, and the magnet60is attached to the frame12in order to detect the rotation of the rear wheel18. In this case, the second detector62transmits the first signal S1to the control device70by wireless communication.

In each of the embodiments, the output of the element64of the second detection device28may be directly input to the control device70, or this may be input to the control device70after amplifying the output of the element64. In this case, the control device70comprises the function of the vehicle speed calculation unit66, and the control device70calculates the second rotational speed NB.

In each of the embodiments, a hub dynamo may be used instead of the magnet60and the element64of the second detection device28. A hub dynamo outputs a periodic signal or a pulse signal every prescribed rotational angle of the front wheel16to the vehicle speed calculation unit66.

In each of the embodiments, it is possible to form the second detection device28of each of the embodiments from a GPS (Global Positioning System) receiver. In this case, the second detection device28or the control device70calculates the second rotational speed NB based on the travel distance per unit of time of the bicycle10, information related to the circumferential length L of the front wheel16, and the gear ratio γ at that time.

In each of the embodiments, it is possible to making the minimum angle of the front wheel16that can be detected by the second detector62of each of the embodiments less than or equal to the minimum angle of the crank32that can be detected by the first detector54. In this case, for example, the first detector54does not comprise a magnet52B or the element56B and has a configuration to detect the position of the magnet52A just once per one rotation of the crank; also, the second detector62is formed comprising a hub dynamo. In this modified example, the accuracy of the rotational speed that is calculated according to the output of the second detector62is higher than the accuracy of the rotational speed that is calculated according to the output of the first detector54. In this case, the control device70may perform the switching operation described above by making the rotational speed that is calculated according to the output of the second detector62the first rotational speed NA and by making the rotational speed that is calculated according to the output of the first detector54the second rotational speed NB.

In each of the embodiments, it is possible to provide a storage unit to which is input a control signal SA that is output from the motor controller82to the control device70, and to detect the gear ratio γ based on the control signal SA that is stored in the storage unit.

In each of the embodiments, it is also possible to change the gear shifting device24to an electric external gear shifting device. The electric external gear shifting device may comprise a front external transmission and a rear external transmission. Additionally, the gear changing device24may be changed to be attached to the crankshaft40. In short, any gear shifting device may be employed as long as the gear shifting device is configured to change the gear ratio γ with a control device70.